1：At five in the afternoon,we took the subway------school

1：At five in the afternoon,we took the subway------school
a.go to b.back to c.going to d.to back to.
请问为什么）
2:In spring,there are many flowers and trees on--------of the West Lake.
a.both sides b.either side c.each side d.every side
（答案是d,但是为什么不能选c）
3.We are talking about the piano and the pianist------were in the concert we attended last night
a.which b.whon c.who d.that
（答案是d,c不行么?）
4.Long,long ago,there lived a very nice king（题目是找long long ago的同义词
）
a.long before b.before a long time c.sometime ago.D.once upon a time
（答案是D,B呢）
5.Please answer my questions--------
a.take turns b.turn by turn c.one after one d.in turn
（答案是d,什么时候用A吖）
6.When he heard the bell,he-----the door
a.hurried off to open b.hurried up to open c.hurried off opening d.hurried up opening.
（答案是a,这种用法怎么用呢）
7.It is warm here--------
A all the year round B.all the year
C． all round the year D.all the years
,C不可以么）