Answer:
D) While the boys played football outside
Explanation:
An adverb clause is a group of words containing a subject and a verb whose function is to modify, describe or add more detail to an adjective, a verb or another adverb. This type of clauses are dependent, therefore, they do not express a complete thought.
Furthermore, an adverb clause often answer questions such as Why? How? When? Where? and In what circumstances? and is introduced by a subordinating conjunction like while, after, since, although, as long as, because, before, even, even though, in order that, wherever, unless and until.
The clause "While the boys played football outside" is an adverb clause because it has all the characteristics mentioned: it does not express a complete thought, it begins with a subordinating conjunction (while), it modifies the verb "danced" and it answers the questions When did the girls dance in the living room? Answer: While the boys played football outside.
