Question

A subordinating conjunction is used to
a. take the place of a coordinating conjunction.
b. separate two independent clauses.
c. join a preposition and a noun or pronoun.
d. introduce a dependent clause.

Answer 1

A subordinating conjunction is used to introduce a dependent clause. The correct answer is D. 
For example: Although he didn't like it, he still had to eat his broccoli. In this sentence, although is the subordinating conjunction used to introduce a dependent/subordinate clause.