The answer is B, "the government is complicated." In the other examples, the subjects and verbs dont match grammatically. For example, in A, the word "forest" should be plural to use the very "are".
B your assignment must be submitted on time
If you mean an adverb clause, I'd say your answer is D. Adverb clauses typically begin with a subordinating conjunction like because, after, if, or although.
I flew up the stairs to my new apartment, opened the door and skipped over the threshold. I examined the room which looked sufficient and felt generous. Excited to get a better view of the surrounding neighborhood, I threw open the windows and was met with a wonderful smell, freshly baked bread. Living next to a bakery would really be amazing. As I sank into the recycled chair in the middle of the room, I wondered what life away from home would be like. I was ready to see what would come next.
