Explanation:

a. Subordinating conjunctions

are used to show the relationship between a dependent clause and an independent clause in a complex sentence. They are used to indicate that the dependent clause is subordinate or secondary in importance to the independent clause. Examples of subordinating conjunctions include: after, although, as, as if, because, before, even though, if, in order that, once, since, so that, though, unless, until, when, where, while, and why.

Answer:

• A. Subordinating conjunctions

is the correct answer, Subordinating conjunctions are used to connect dependent clauses to independent clauses and indicate the relationship between them, for example "Although it's raining, we will go for a walk.".