Complete the space tourist's postcard back to Earth. Drag the correct words into the gaps.
The zero-gravity pool, which is located on the top deck, is incredibly fun to float around in. The alien staff members who run the gift shop are very friendly, even if they have six tentacles each. I bought a lot of souvenirs because everything that they sell is made of genuine moon rock!
The zero-gravity pool, which is located on the top deck, is incredibly fun to float around in.
Because this is a non-defining relative clause (set off by commas) describing a thing, we must use which. Where would require a subject to follow it (e.g., where I swim).
The alien staff members who run the gift shop are very friendly...
We use who for people (or personified beings like intelligent aliens) when they are the subject of the relative clause.
...everything that they sell is made of genuine moon rock!
After indefinite pronouns like everything, anything, nothing, or all, we strongly prefer that over which. What cannot be used as a relative pronoun following a noun or indefinite pronoun.
Relative clause
A relative clause is a dependent clause that modifies a noun, typically introduced by a relative pronoun (who, whom, whose, which, that) or relative adverb (where, when, why). The man who lives in this house has not been seen for days. They split into restrictive (essential to the meaning, no commas) and non-restrictive (extra information, set off by commas).
The split matters because the comma changes the meaning: My brother who lives in Paris (one of several brothers) vs. My brother, who lives in Paris, (my only brother). Getting comma placement right is one of the highest-leverage moves at B2+.
Pronoun
A pronoun is a small, closed class of words that stands in for a noun or noun phrase. The main types: personal (I, you, he, she, it, we, they) plus their object (me, him) and possessive (my, mine) forms; demonstrative (this, that); relative (who, which, that); interrogative (who, what); and reflexive (myself, yourself).
Pronouns are how English avoids endlessly repeating names. The catch: their meaning depends entirely on context, so unclear pronoun reference (Tom told Mike that he was wrong — who's he?) is one of the most common writing problems.
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.
Punctuation
Punctuation is the set of visual marks — periods, commas, question marks, colons, semicolons, apostrophes, quotation marks, hyphens and dashes — that show readers where sentences begin and end, where pauses go, and how parts of a sentence relate.
Punctuation does two jobs: it follows the rhythm of speech (where you'd pause aloud) and it marks the structure of clauses. Mismatch the two and writing reads either as breathless or as choppy. Mastering the basics is a small investment with huge returns — clear punctuation makes prose look careful and considered.
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.