问题详情

In the passage, the author wants to tell us ______.
A．that people dreamed of leaving their home planet and exploring other worlds became reality
B．after the Apollo program, the emphasis in piloted missions shifted to short-duration spaceflight
C．space exploration is a great challenge to human beings and will be achieved through generation"s work
D．today efforts focus on keeping people healthy during space missions and in increasing the cost of sending satellites into orbit