I voted Marcus off the island because he ate the last hidden mango.
"Because" introduces the reason. "So" would incorrectly introduce a result, and "therefore" is a conjunctive adverb that requires different punctuation (usually a semicolon).
Since we had all agreed to share the secret food stash, his betrayal was absolutely unforgivable.
"Since" correctly introduces a dependent adverb clause at the beginning of the sentence. "Therefore" and "Consequently" cannot be used to join a dependent clause to an independent clause in this way.
I feel absolutely no guilt about my decision, as he would have done the exact same thing to me!
"As" is a subordinating conjunction introducing the reason. "Due to" is a preposition and cannot be followed by a full clause.
Clause
A clause is a grammatical unit built around a verb — typically a subject plus a predicate (She laughed; The manager approved the budget). Clauses come in two types: independent clauses stand alone as complete sentences; dependent clauses need an independent clause to make sense (Because I overslept — incomplete on its own).
Spotting clause boundaries is the foundation of correct punctuation. Once you can see where one clause ends and another begins, comma rules, run-on sentences, and complex sentence structure stop being mysteries.
Dependent clause
A dependent clause (also called a subordinate clause) is a clause that has a subject and a verb but can't stand alone as a complete sentence. It needs an independent clause to attach to. Because I overslept is a dependent clause; I missed the bus because I overslept is a complete sentence.
Dependent clauses come in three main types: noun clauses (acting as a noun: I know that he likes me), adjective/relative clauses (modifying a noun: the dwarf who has no beard), and adverbial clauses (modifying a verb or whole clause: Wherever she goes). They're how English packs more information into a single sentence.
Conjunction
A conjunction is a word that connects other words, phrases, or clauses. English has two main types: coordinating conjunctions join units of equal weight (and, but, or, so, yet, for, nor — the FANBOYS), while subordinating conjunctions introduce dependent clauses (because, although, if, when, while, since, unless).
Conjunctions are how you build compound and complex sentences instead of stacking short ones. The choice of conjunction signals the relationship between the ideas — addition, contrast, cause, condition, time — so picking the right one shapes the whole meaning.
Complex sentence
A complex sentence combines an independent clause with at least one dependent (subordinate) clause: I missed the bus because I overslept. The dependent clause adds extra information — usually about time, reason, condition, or which thing is meant — but can't stand alone. It's introduced by a subordinating conjunction (because, although, if, when, while) or a relative pronoun (who, which, that).
Mastering complex sentences is the move from simple, choppy writing to prose that links ideas. It's also where comma decisions get interesting — placement depends on which clause comes first.
Adverb
An adverb modifies a verb, an adjective, or another adverb — adding information about how, when, where, how often, or to what degree something happens: she sings beautifully, unbelievably fast, we go there often. Many adverbs end in -ly, but plenty don't (well, fast, hard, almost).
Adverbs matter because they're how you add nuance without piling on extra clauses. Used well, a single adverb can sharpen a vague sentence (she answered → she answered honestly), but misplace one and the meaning drifts in a way native speakers immediately notice.
Humor
The Humor tag marks questions and challenges where the author has tried — subjectively, deliberately — to make the practice itself entertaining. Expect characters, scenarios, and storylines that play with absurdity: zombies, alien tourists, a chef's disaster, a roommate's complaint. The grammar rule is real; the wrapping isn't.
Humor matters because grammar drills are forgettable. Tying a rule to a story your brain wants to keep makes it stick. Filter by Humor when motivation is what you're short on, not study time.
B2 | Upper Intermediate
B2 is the upper-intermediate level in the CEFR framework, sitting between B1 and C1. At B2 you can read editorials, follow most TED talks without subtitles, and hold extended conversations on abstract topics — including topics outside your everyday life.
Grammatically, B2 means flexible control of mixed conditionals, passive voice across tenses, reported speech with proper backshifting, and participle clauses. B2 is the standard target for university entrance exams (IELTS 5.5–6.5, TOEFL 87–109) and most skilled-migration thresholds — knowing whether you're there shapes your study plan.
Difficulty: Medium
The Medium difficulty tag marks questions and challenges in the middle of the difficulty range — typically suitable for A2 to B1 learners. Expect a single rule with realistic distractors, longer sentences, and contexts where you have to think before answering rather than reading off the obvious choice.
Filter by Medium when you're past the absolute basics and ready to consolidate. It's the level where most lasting progress happens — easy enough that you can finish without exhausting concentration, hard enough that getting it right means you've actually understood.