Complete the starship captain's slightly embarrassing log entry by selecting the correct conjunction.
We had to land on the swamp planet ___ our ship's hyperdrive was making a sound like a dying washing machine.
The correct answer is as.
As can be used as a subordinating conjunction meaning "because" to introduce an adverb clause of reason. "So" introduces a result, "because of" requires a noun phrase instead of a full clause, and "nevertheless" shows contrast.
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.
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.
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.
Complex sentence
Complex vs compound sentence: a compound sentence links two equal independent clauses with and/but/or. A complex sentence links an independent clause with a subordinate (dependent) clause — one idea is the main point, the other is background.
A complex sentence = independent clause + dependent clause. The dependent clause adds time (when), reason (because), condition (if), or detail (who/which).
Diagnostic: are both halves able to stand alone? Yes → compound. Can only one stand alone? → complex.
B2 | Upper Intermediate
B2 vs C1: B2 means effective communication on complex topics with some effort. C1 means effortless fluency with precise register control. If you can argue a point but still reach for words and make structural slips under pressure, you're B2.
B2 is the upper-intermediate CEFR level: mixed conditionals, complex passives, reported speech with backshift, participle clauses, and sustained written argument.
Diagnostic: does your writing read as "competent non-native" or "could be native"? The former → B2. The latter → C1.
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.