The author's attitude towards intelligent seem to be that_____.

A．the progress in biography is so great that people feel astonished
B．the progress in cryogenics is so great that people feel astonished
C．the progress in information technology has great influence on human
D．the progress in information technology is beneficial to human

A．The challenge was developing rockets powerful enough and reliable enough to boost a satellite into orbit.
B．The challenge was building the satellites themselves.
C．Engineers also had to build tracking stations to maintain radio communications with these artificial "moons" as they circled the planet.
D．The development of rockets and satellites.