Commas That Change Meaning: correct answers
Jump to answers ↓Defining the Noun vs. Adding Extra Details
When we use relative clauses (phrases starting with who, which, or where), commas tell the reader whether the information is essential to identifying the noun, or if it's just a bonus detail.
If a clause has no commas, it is essential (restrictive). It tells us exactly which person or thing we are talking about out of a larger group. If a clause is surrounded by commas, it is non-essential (non-restrictive). The listener already knows exactly who or what you mean, and you are just dropping in an extra fact. You could delete the phrase inside the commas, and the sentence would still make perfect sense.
How Commas Change the Reality of a Sentence
Let's look at how adding or removing commas changes facts—like how many siblings you have, or how many people were involved in a crime.
Imagine a detective is tracking a group of ten suspects, but only three of them are wearing red hats.
❌ The suspects, who were wearing red hats, escaped. (Incorrect for this context! The commas mean there are no other suspects; all ten were wearing red hats, and all ten escaped.) ✅ The suspects who were wearing red hats escaped. (Correct! The lack of commas specifies that only the three wearing red hats escaped. The others did not.)
The exact same rule applies to family members. If you have three brothers, you must use an essential clause (no commas) to specify which one you mean:
✅ My brother who lives in Paris is terrified of baguettes.
If you use commas ("My brother, who lives in Paris, is terrified of baguettes"), the grammar implies that you only have one brother in total, and the fact that he lives in Paris is just a bonus detail.
Saving Lives with the Vocative Comma
Commas also change meaning when you speak directly to someone. This is called the "vocative comma" or direct address. Whenever you use a person's name, title, or group noun to get their attention, you must separate it from the rest of the sentence with a comma. Without it, the person might accidentally become the object of your verb!
Imagine a chef is texting his kitchen team to start the dinner service.
❌ Let's serve the team! (Incorrect—this means the team is the food being served to the customers.) ✅ Let's serve, team! (Correct—the chef is talking directly to the team, telling them it is time to work.)
A Common Trap: Using "That" with Commas
A frequent mistake for English learners is using the relative pronoun that inside a comma-separated clause. While who and which can be used with or without commas depending on the meaning you want to convey, that can never be used after a comma in a relative clause.
Imagine you are describing a specific car you have already identified to your friend.
❌ My new car, that I bought yesterday, is incredibly fast. ✅ My new car, which I bought yesterday, is incredibly fast.
If you want to use that, you must remove the commas and make the information essential to identifying the noun:
✅ The car that I bought yesterday is incredibly fast.
Correct answers
Question 1
Help the detective write her warning accurately! She wants to text her team that only the suspects wearing red hats are dangerous (the suspects in blue hats are totally harmless).
Choose the sentence that expresses this exact meaning.
The correct answer is The suspects who are wearing red hats are highly dangerous.
To specify which suspects are dangerous, you need a defining relative clause, which does NOT use commas. This tells us we are only talking about a specific group of suspects.
The sentence with commas ("The suspects, who are wearing red hats, are highly dangerous.") would mean that all the suspects are wearing red hats, and all of them are dangerous! The options with only one comma are grammatically incorrect because you cannot separate a subject from its verb with a single comma.
Question 2
The correct answers are It's time to eat, everyone! and Let's start serving, guys!
The vocative comma (or comma of direct address) is used when speaking directly to someone. Without the comma in "Let's cook Mom!", "Mom" becomes the object of the verb "cook"—meaning she is the meal! Adding a comma ("Let's cook, Mom!") saves lives by showing you are talking to her.
Question 3
Help the detective complete her case notes by dragging the correct meaning to match each witness statement. Pay close attention to the commas!
Witness A stated: "The suspects who wore red hats fled the scene."
According to grammar rules, this means that only some of the suspects wore red hats and ran away.
Witness B stated: "The suspects, who wore red hats, fled the scene."
According to grammar rules, this means that all of the suspects wore red hats and ran away.
Witness A stated: "The suspects who wore red hats fled the scene."
This means that only some of the suspects wore red hats and ran away.
Without commas, the clause "who wore red hats" is restrictive (defining). It tells us exactly which specific suspects fled, implying there were other suspects present who did not wear red hats.
Witness B stated: "The suspects, who wore red hats, fled the scene."
This means that all of the suspects wore red hats and ran away.
With commas, the clause "who wore red hats" is non-restrictive (non-defining). It simply adds extra, descriptive information about the suspects, implying that all the suspects in question wore red hats and fled.
Question 4
The correct answers are The clients only looked at one specific house during the tour. and The fact that the house has a swimming pool is just an extra, bonus detail.
By using a comma, the agent created a non-defining (non-restrictive) relative clause. This means we already know which house she is talking about (likely because they only visited one), and the pool is just extra information. If she had left out the comma ("the house which has a swimming pool"), it would mean they visited multiple houses and she needed the pool detail to specify which house they liked.
Question 5
- Only a specific group of aliens was captured (the ones doing a silly dance—the others got away!).
- All the scientists were terrified (and as an extra, non-essential detail, they were all hiding).
The aliens who were dancing the Macarena were captured by the security team. Meanwhile, the scientists**, who were hiding under their desks,** watched in absolute terror.
Why no commas for the aliens?
When you need to specify which people or things you are talking about out of a larger group, you use a restrictive relative clause (no commas). The guard only caught the dancing aliens, not all of them!
Why commas for the scientists?
When you are just adding extra, bonus information about a group that is already fully identified (all the scientists), you use a non-restrictive relative clause (with commas). If you remove the phrase between the commas, the main sentence "the scientists watched in absolute terror" still makes perfect sense.
Question 6
The correct answers are There were multiple suspects at the scene, but only a smaller group of them escaped. and The phrase "who were wearing red hats" is essential information needed to identify exactly who ran away.
Because there are no commas, this is a defining (restrictive) relative clause. It tells us which specific suspects escaped out of a larger group. If the witness had used commas ("The suspects, who were wearing red hats, escaped."), it would mean all the suspects escaped, and the hats were just a bonus detail!
Question 7
Maya: I'm visiting my sister who owns a bakery next week. The other two are so jealous!
Leo: Have fun! My brother**, who hates sweets,** is coming to stay with me, so I'll be eating broccoli all week.
Because Maya has three sisters, she must use a restrictive relative clause (no commas) to tell us which sister she is visiting. The phrase "who owns a bakery" is essential information.
Because Leo has only one brother, we already know exactly who he is talking about. The fact that his brother hates sweets is just extra information, so it goes inside a non-restrictive relative clause (separated by commas).
Question 8
Complete the eccentric scientist's journal by dragging the correct interpretation to match his notes about his test subjects.
Note 1: "The zombies who ate their vegetables are allowed inside the bunker."
Interpretation: This means that only the healthy zombies can come in.
Note 2: "The zombies, who ate their vegetables, are allowed inside the bunker."
Interpretation: This means that every single zombie can come in.
Note 1: "The zombies who ate their vegetables are allowed inside the bunker."
Interpretation: This means that only the healthy zombies can come in.
Without commas, the relative clause "who ate their vegetables" restricts the noun. It identifies exactly which zombies are allowed inside (only the ones that ate their veggies!).
Note 2: "The zombies, who ate their vegetables, are allowed inside the bunker."
Interpretation: This means that every single zombie can come in.
Commas make the clause non-restrictive. It means all the zombies are allowed inside, and the fact that they ate their vegetables is just a fun piece of extra information!
Question 9
Read the comedian's joke setup and choose the correct interpretation based on the punctuation.
"My brother, who lives in Paris, is terrified of baguettes."
Based on the commas in this sentence, what do we know about the comedian's family?
The correct answer is The comedian has exactly one brother.
The commas create a non-defining relative clause, which means "who lives in Paris" is just extra, bonus information. We only use this structure when it's already perfectly clear who we are talking about—which implies the comedian has only one brother!
If the comedian had multiple brothers, he would remove the commas ("My brother who lives in Paris...") to specify which brother he meant.
Question 10
Help the HR manager understand the company newsletter. Read the sentence below and choose the statement that correctly describes its meaning.
"The developers, who fixed the server crash, were given an extra week of vacation."
The correct answer is All the developers fixed the server crash and got extra vacation.
The commas make this a non-defining relative clause. This means the clause just adds extra, descriptive information about "the developers" as a whole group. It implies that all the developers fixed the crash and got the vacation!
If there were no commas ("The developers who fixed the server crash..."), it would be a defining relative clause, meaning only a specific subgroup of developers got the vacation.