The correct answers are Both of my eyebrows were singed off by the blast, Half the laboratory is covered in green slime, and All of the bubbling potions evaporated instantly.
With the quantifiers all, both, and half, the word "of" is optional when followed by a noun phrase with a determiner (e.g., Half the laboratory OR Half of the laboratory).
However, there are two strict rules:
- If you use a pronoun, you must include "of" (e.g., All of them, NOT All them).
- If you use "of" before a noun, you must include a determiner like "the" or "my" (e.g., Half of the laboratory, NOT Half of laboratory).
Determiner
A determiner is a word that comes before a noun to clarify what it refers to: which one, how many, whose. The English determiners include articles (a, the), demonstratives (this, that), possessives (my, your), quantifiers (some, many, few), and distributives (each, every).
Most singular countable nouns in English require a determiner — I bought book is wrong; you need I bought a book or I bought the book. Determiner choice signals how much information you assume the listener already has, so getting it right shapes how natural your speech and writing sound.
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.
Phrase
In grammar, a phrase is a group of words (sometimes a single word) that functions as a single unit in a sentence — but doesn't include a subject + verb pair the way a clause does. Common types: noun phrase (the old red car), verb phrase (has been running), prepositional phrase (on the table), adjective phrase (incredibly tired), adverb phrase (very quickly).
Phrases are the building blocks between individual words and full clauses. Recognising them helps you see how sentences hold together — and where you can break, expand, or rearrange them without losing meaning.
Article
Articles are a small group of determinatives that signal whether a noun refers to something specific (the book) or something general (a book). English has three: the definite article the, the indefinite articles a/an, and the zero article — the meaningful absence of any article (Coffee keeps me awake).
Articles are one of the trickiest parts of English for non-native speakers because the choice depends on context, not just the noun itself. Get them right and your writing instantly sounds more natural; miss them and even simple sentences feel "off" to a native ear.
Noun
A noun is a word that names something — a person, place, thing, idea, action, or quality. Nouns are one of the open word classes in English, alongside verbs, adjectives, and adverbs. They typically appear as the subject or object of a clause, after articles or adjectives, and as the head of a noun phrase.
Recognising nouns reliably is the foundation for nearly every other grammar topic — agreement, articles, plurals, possessives, and prepositions all depend on it. Get this right and the rest of English grammar starts to fall into place.
C1 | Advanced
C1 is the advanced level in the CEFR framework, sitting between B2 and C2. At C1 you stop translating in your head and start thinking in English — handling specialised articles outside your field, picking up implicit meaning, and writing structured arguments on complex topics.
Grammatically, C1 means natural use of inversion (Rarely have I seen…), mixed and advanced conditionals, subjunctive forms in formal contexts, and cleft sentences for emphasis. Most university programmes for non-native speakers and many professional certifications set C1 as their entry standard.
Difficulty: Hard
The Hard difficulty tag marks questions and challenges aimed at upper-intermediate to advanced learners — typically B2 and above. Expect interacting rules, edge cases, distractors that look right at first glance, and contexts where the surface meaning and the grammatical answer don't match.
Filter by Hard when you're past the basics and want material that genuinely tests your understanding. These questions catch the gaps your textbook didn't — register-sensitive choices, exception cases, mixed conditionals, the difference between would have been and had been.