The correct answers are It's been a long day at work, Whose umbrella is this?, The company changed its logo last year, and Who's coming to the party tonight.
"It's" = it is or it has (contraction), "its" = possessive (belonging to it). "Who's" = who is or who has (contraction), "whose" = possessive (belonging to whom). In "The dog wagged it's tail," the possessive "its" is needed. In "Who's turn is it," the possessive "whose" is needed.
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.
Auxiliary verb
An auxiliary verb (or "helping verb") is a verb that combines with a main verb to add grammatical meaning — questions, negation, tense, aspect, voice, or modality. The English auxiliaries are forms of be, have, do, plus the modal verbs (can, could, will, would, should, may, might, must).
Auxiliaries are what let you build past tense (have gone), continuous aspect (is going), passive voice (was eaten), and questions (Do you know?). Without them, you can't form most of the structures you need beyond the simple present and past — they're the engine that powers half the tense system.
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.
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.
Vocabulary
The Vocabulary tag groups practice that focuses on words rather than grammar rules — common words, collocations, phrasal verbs, idioms, and the lexical patterns native speakers reach for instinctively. It cuts across grammar topics, offering targeted vocabulary work at every CEFR level from A1 to C2.
Grammar gets you the structure of English; vocabulary gets you the colour. Plenty of B1 grammar with A2 vocabulary still sounds simple; the right word at the right register is what shifts your English from "correct" to "natural".
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.