Help the dedicated university student complete her text to her roommate.
"Don't wait up for me! I plan to stay at the library studying ______ it closes at midnight."
The correct answer is until.
The conjunction until is used to show that a continuous action ("stay at the library") goes on up to a specific point in time ("it closes at midnight"). The other options do not logically fit the continuous nature of the verb "stay."
Conjunction
Coordinating vs subordinating conjunction: coordinating (and, but, or) joins two elements of equal rank — clause + clause, noun + noun. Subordinating (because, although, if) makes one clause depend on the other. The test: remove the conjunction. If both halves still feel complete → coordinating. If one half collapses → subordinating.
Conjunctions are connecting words for clauses, phrases, and words. The choice between coordinating and subordinating determines whether you're building a compound or complex sentence.
Diagnostic: does the conjunction create a dependent clause? Yes → subordinating. Does it link equals? → coordinating.
Clause
Clause vs phrase: a clause has a subject + verb (she runs); a phrase does not (in the morning, running fast). This is the first distinction to make when analysing sentence structure.
A clause is a grammatical unit built around a verb: independent clauses make complete sentences; dependent clauses attach to them as modifiers or complements.
Diagnostic: find the verb. If there's a subject doing or being something → clause. If there's no subject-verb pair → phrase.
Dependent clause
Dependent vs independent clause: an independent clause stands alone as a sentence (I was tired.). A dependent clause has a subject + verb but cannot stand alone (Because I was tired. ❌). The subordinating word is what makes it dependent — remove it and the clause becomes independent.
A dependent clause is introduced by a subordinating conjunction or relative pronoun and functions as an adverb, adjective, or noun inside a larger sentence.
Diagnostic: strip the opening word (because, if, who, which). Does the remainder work as a sentence? Yes → the original was dependent (the subordinator trapped it). No → deeper structural issue.
B1 | Intermediate
B1 vs B2: B1 handles standard everyday communication and simple opinions. B2 handles abstract topics, sustained arguments, and nuanced register. If you can chat about your life but struggle to debate an issue or write a formal essay, you're B1.
B1 is the intermediate CEFR level: independent handling of familiar topics, second conditional, basic passive, reported speech, and linking words for cause and contrast.
Diagnostic: can you read a newspaper article on a familiar topic and summarise the argument? Comfortably → B2. Struggle with abstractions → still B1.
Medium
Medium vs Easy: Easy has one obviously correct answer and clearly wrong distractors. Medium has one correct answer but plausible distractors — you need to actually know the rule, not just guess from sound.
The Medium tag filters for A2–B1 challenges with realistic difficulty: one rule per question, plausible alternatives, everyday contexts.
Diagnostic: if you're scoring 90%+ on Easy, move here. If you're below 60% on Medium, go back to Easy for that topic. Target 70–80% accuracy for maximum learning.