The correct answers are We are looking at a house whose roof is entirely made of pancake batter and Meet the landlord whose cats have their own dedicated bedrooms.
Whose is a possessive relative pronoun. Unlike who (which only refers to people), whose can be used to show possession for both animate beings (the landlord) and inanimate objects (the house).
Who's is a contraction for who is or who has; it cannot be used to show possession. Furthermore, "of which its" is redundant and grammatically incorrect; the proper phrasing would simply be "whose doors" or "the doors of which."
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.
Possessive
The possessive form shows ownership or association in English. With most nouns, you add 's (Sarah's book, the dog's tail); with plural nouns ending in s, you add just an apostrophe (the students' essays). Pronouns have irregular possessives — both possessive determiners (my, your, his, her, our, their) and possessive pronouns (mine, yours, his, hers, ours, theirs).
The most-mixed-up pair: its (possessive of it) vs it's (= it is). Possessive its takes no apostrophe; it's always means it is or it has. Getting this right is one of the highest-leverage punctuation moves in English.
Apostrophe
The apostrophe ( ' ) is a punctuation mark with two main jobs in English: marking missing letters in contractions (do not → don't, they are → they're) and showing possession with nouns (the eagle's feathers, one month's time). It's not used for plurals — cats never takes an apostrophe, even though many writers slip and add one.
Mixing up its (possessive) and it's (contraction of it is), or writing banana's £1 on a market sign, are the giveaway errors that mark a writer as careless. Getting the apostrophe right is one of the highest-leverage punctuation skills you can learn.
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.
B1 | Intermediate
B1 is the intermediate level in the CEFR framework — the point where you stop relying on memorised phrases and start handling everyday English independently. At B1 you can describe experiences, explain opinions, and follow most clear standard speech on familiar topics like work, travel, and hobbies.
Grammatically, B1 means combining tenses with precision, building complex sentences, and starting to use passive voice, modal verbs for necessity and possibility, and verb patterns (gerund vs. infinitive). Knowing your level shapes what you study next: pushing too far ahead frustrates you; staying below your level wastes time.
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.