听力原文:Ever since the Apollo moon landings, the idea of human expeditions to the Mars ha
Why have the Americans developed space shuttle according to the passage?
A.It is a first step to explore outer space.
B.It is a follow-up action of the Apollo moon landings.
C.It is a compromise to the exorbitant human expeditions to the Mars.
D.It is a compensation for the wishful thinking of human landing on the Mars.