Question

Complete the sentence with a suitable adverb clause:
We can enter the airport .

• A. after the verification of our passports
• B. only in the mornings
• C. since our passports have been verified
• D. none of the above

Answer 1

The correct option is C since our passports have been verified

An adverb clause is a group of words containing a subject and a verb, and it functions as an adverb, by modifying an adjective, verb or an adverb. Adverb clauses generally begin with a subordinate conjunction (since, because, while, etc.).
Option C is correct because it is an adverb clause of reason, 'since' is a conjunction that refers to cause or reason: "passports have been verified".
Option A is incorrect because it is a phrase, not an adverb clause.
Similarly, option B is incorrect because it is a phrase, not a clause.
Option D is incorrect because the answer lies in C.