You__him so closely;you should have kept your distance.
You__him so closely;you should have kept your distance.
shouldn't follow mustn't follow
couldn't have been following shouldn't have been following
_____from space,the earth,with water___20% of its surface,looks like a "blue ball".
Seen covered
Seeing covering
Seeing covered
Seen covering
第一题为什么不能用shouldn't follow