The anser is D: compound. A compound sentence is when two or moreindependent clauses that have related ideas are joined with a coordenator (for, and or but) or a semicolon. Independent clauses can stand alone as a complete thought. They are not dependent of one another to express a complete thought, but they join similar ideas.
Because the longer the focal length, the smaller the patch of sky you're observing. But a longer focal length also gives a higher possible magnification.
