The type of sentence given is a compound sentence. It is a compound sentence because it consists of two independent sentences: "I already said yes to someone else" and "I can't go to the dance with you". In order to link the two sentences, the conjunction "because" is used.
Answer:
D.
is one of the hardest workers he has ever seen
Explanation:
This is an excerpt from <em>Into the Wild</em>, “I’ve given jobs to lots of hitchhikers over the years, ' says Westerberg. 'most of them weren’t much good, didn’t really want to work. It was a different story with Alex. <em>He was the hardest worker I’ve ever seen."</em>