6．登陆火星似乎只是个梦想。

5．既然火星与地球完全不同，如果我们计划有朝一日去火星的话，我们就要带上氧气、食品、衣服和住的地方。(shelter)

4．这样我们就不能在那里生活了。　 (prevent...from)

3．人类对火星有了一些了解：火星上没有氧气，火星上中午的温度可能在50度左右，而晚上则在零下100度左右了。(know a little about)

2．我们能否登陆火星完全取决于科学技术的发展。(depend on)

1．我们不知道火星上是否有生命。(whether，exist，life)

12．China is a ________ country，while America is a ________ country.(develop)

答案：1.energy　2.violence　3.independent　4.disappointment　5.presence　6.harm　7.lessen　8.cheerful　9.weightless　10.Exhausted　11.development　12.developing，developed

11．The ________ of this industry will take several years.(develop)

10．________ though she was，there was no hope of her being able to sleep.(exhaust )

9．It is known to all that man is ________ in space.(weight )