One of my best friends...
The phrase "one of" must always be followed by a plural noun, because you are singling out one person or thing from a larger group.
...the modern furniture...
"Furniture" is an uncountable noun in English. It never takes an "s" at the end, even when you are talking about multiple chairs, tables, and sofas!
...each of the decorators wants...
The pronoun "each" is singular, so it requires a singular verb ("wants"), even though it is followed by a plural noun phrase ("of the decorators").
Grammatical number
If you've ever written The data shows and been told it should be The data show — or written The list of items are when it should be is — you've hit a grammatical-number trap. Number agreement looks simple in theory (one takes singular, more than one takes plural) but English has enough irregular plurals and tricky collective nouns to keep you on your toes.
Grammatical number is the singular/plural distinction on nouns, pronouns, and verbs. Most English nouns form plurals with -(e)s; pronouns have irregular pairs (I/we, he/they); verbs agree with their subject (He goes vs They go).
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.
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.
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.