Question

Supply a suitable adverb clause to complete the sentence:
He believes in violence and war, .

• A. because of his mentor
  
• B. yet he does not propagate it
• C. whereas his brother believes in peace and harmony
  
• D. none of the above

Answer 1

Answer: (C)

whereas his brother believes in peace and harmony

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 concession or contrast, 'whereas' is a conjunction that refers to the contrast ideas: 'violence and war' and 'peace and harmony'.
Option A is incorrect because it is not an adverb clause; 'because of his mentor' is an adverb phrase that refers to cause or reason.
(An adverb phrase does not contain a subject or a verb, or both, whereas an adverb clause contains a subject and a verb.)
Option B is incorrect because it is a coordinate/independent clause whereas an adverb clause is subordinate/dependent.
Option D is incorrect because the answer lies in C.