The correct answers are One of the suspects is hiding in the bakery. and One of the bakers is acting very suspiciously.
The phrase "one of the..." must be followed by a plural noun because you are singling someone out from a larger group (e.g., suspects, bakers). However, the verb must be singular (e.g., is) because the actual subject of the sentence is the singular word "One."
Subject
If you've ever written The list of items are wrong (should be is wrong) — you've hit the subject-agreement trap. The subject is list, not items, and the verb has to agree with it. Long sentences with prepositional phrases between the subject and verb are where this most often goes wrong, and getting it right is what stops careful readers from flagging your writing.
The subject is the part of a sentence or clause that says who or what the sentence is about. Typically a noun, pronoun, or noun phrase before the verb, controlling the verb's number and person.
Verb
If grammar feels overwhelming, the fix is almost always to focus on verbs first. They carry the action, the time, the mood, and the voice — a single verb form decides whether your sentence reads as past or present, fact or hypothetical, active or passive. Get verbs solid and the rest of grammar suddenly looks much smaller.
A verb expresses action, state, or occurrence — the engine of every English sentence. Most verbs have five forms (base, -s, past tense, past participle, -ing); be has eight; modal verbs have fewer. Verbs carry tense, aspect, mood, and voice.
Noun
If you've ever frozen mid-sentence wondering whether to say an information or some information, child or children, they or them — you've hit the core of how English uses nouns. Nail this down and articles, plurals, possessives, and pronoun choice all stop feeling like guesswork.
A noun is a word that names something: a person, place, thing, idea, action, or quality. Nouns are the building blocks every other part of speech bolts onto. Spot one in a sentence and you can usually predict the article, the verb form, and the pronouns that follow.
Phrase
If you've ever read a long sentence in English and felt lost in the middle, you've hit a sentence with too many phrases stacked together. Learning to spot phrases — on the table, the man with the hat, very quickly — turns dense prose into something you can parse: each phrase is one chunk of meaning, not a string of unrelated words.
A phrase is a group of words functioning as a single unit in a sentence, without a subject + verb pair (which would make it a clause). Types include noun phrase (the red car), verb phrase (has been running), prepositional phrase (on the table), and adjective/adverb phrases.
Progressive tense
If you've ever paused over I work in London vs I'm working in London and not been sure which to pick — you've hit the simple/progressive distinction. The first means it's your usual job; the second means it's temporary, going on right now. Native speakers reach for this distinction constantly without thinking; learners have to make it deliberate.
The progressive aspect marks ongoing action at a time of reference, formed with be + -ing: I am working, She was reading, They will be travelling. Marks temporary or in-progress events. Stative verbs (know, believe, own) don't normally take it.
B2 | Upper Intermediate
If a university admissions team or visa office has ever asked you for an English test score, B2 is probably the level they had in mind. It's the threshold where your English stops being a constraint and starts being a tool — and the line between B1 and B2 is often the line between "stuck in beginner classes" and "ready to study or work in English."
B2 is the upper-intermediate level in the CEFR framework, demanding flexible control of mixed conditionals, passive voice across tenses, reported speech with backshifting, and participle clauses.
Difficulty: Medium
If easy questions feel too obvious but hard questions leave you guessing, you're probably ready for Medium — the level where most real learning happens. It pushes just enough to expose the rules you don't quite have yet, without burying you in edge cases. This is where steady fluency is built, one well-aimed challenge at a time.
The Medium difficulty tag marks middle-range challenges — typically A2 to B1. One rule per question, realistic distractors, and contexts that require active thought rather than instant recognition.