1.——Shall we go on a picnic this weekend?
——Good idea,unless it _______
A.rains B.will rain C.doesn't rain D.won't rain
2.——There was too much destroying weather this year.
——Yes,that's a serious problem.People_______protect the earth well.
A.have to B.must C.will D.can
3.He isn't the man _______I spoke to in the classroom.
A./ B.which C.whose D.where
4.All the information you need is on the Internet.Get online,and you will get _______.
A.them B.one C.it D.those
5.The places _______ the animals lived many years ago have changed a lot.
A.where B.which C.that D./
6.You'd better start out early _______ you can make it.
A.even though B.as if C.what if D.so that
7.The river is more than _______ .
A.twenty meter wide B.twenty meters wide
C.twenty meter of wide D.wide of twenty meter
8.It is difficult for us to learn a lesson in life _______we've actuallyhad that lesson.
A.when B.after C.since D.until
第五个问题是定语从句吗?如果是，请帮我讲一下相关的知识！