The correct answers are The security guard was asleep at his desk. and The shiny diamond disappeared exactly at midnight.
Every English clause needs exactly one subject. If you already have a noun acting as the subject (like "The museum director" or "My partner"), adding a pronoun (like "she" or "he") right after it creates a "double subject" error.
Some languages drop pronouns entirely because the verb endings do all the heavy lifting. In English, we must use a subject, but we only need to state it once!
Subject
The subject is the part of a sentence or clause that tells you who or what the sentence is about. It's typically a noun, pronoun, or noun phrase that comes before the verb and controls the verb's form: She works (singular) vs They work (plural).
The subject isn't always the doer of the action — in passive sentences, it receives the action (The window was broken). English also uses dummy subjects like it and there that hold the subject slot without carrying real meaning (It is raining; There are problems). Spotting the real subject is what makes subject-verb agreement automatic.
Word Order
Word order is the sequence in which words appear in a sentence. English is fundamentally an SVO language — subject, verb, object (Kate loves Mark). The order of adjectives, adverbs, and modifiers within a noun phrase also follows fixed patterns (a small red wooden box, not a wooden red small box).
In English, word order carries grammatical meaning — change the order and you change the sentence. The dog bit the man and The man bit the dog differ only in word order, but the meaning flips entirely.
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.
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.
Sentence
A sentence is the largest grammatical unit in writing — one or more clauses expressing a complete thought, ending with a period, question mark, or exclamation mark. English sentences come in four structural types: simple (one independent clause), compound (two or more independent clauses joined), complex (independent + dependent clause), and compound-complex (multiple independent + dependent clauses).
Mastering sentence types is what lets you vary rhythm in writing. All-simple sentences read as choppy; all-complex sentences read as dense. Mixing them is what makes prose breathe.
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.