The stars, some of them at tremendous speeds, are in motion just as the planets are, yet being *so far away from the Earth that their apparent positions in the sky do not change enough for their movement to be observed during a single human lifetime.
A) The stars, some of them at tremendous speeds, are in motion just as the planets are, yet being
B) Like the planets, the stars are in motion, some of them at tremendous speeds, but they are
C) Although like the planets the stars are in motion, some of them at tremendous speeds, yet
D) As the planets, the stars are in motion, some of them at tremendous speeds, but they are
E) The stars are in motion like the planets, some of which at tremendous speeds are in motion but
我的问题点和之前的不太一样：为什么不能选D？D项用as有什么问题？OG解释说as必须引导一个从句----什么时候有这样的规定？还是说我的理解有问题？
谢谢各位牛人！！！
-- by 会员 leexiaomi2011 (2011/5/14 15:18:18)