we all know that___walking on the moon is very difficult.a.one b the c./ d.a 选哪个为什么?

问题描述:

we all know that___walking on the moon is very difficult.
a.one b the c./ d.a
选哪个为什么?

b 因为walking是指定的 所以用b

we all know that a walking on the moon is very difficult
我们都知道,在月球上行走是非常困难的