句型转换。

1．Molly was singing at that time．(改为一般疑问旬)

________ Molly ________ at that time?

2．The Greens have worked in China for four years．(对划线部分提问)

________ ________ have the Greens worked?

3．Last year．we planted 110 trees．(改为现在完成时)

So far,we ________ ________ 110 trees．

4．Mary has learnt Italian before．(改为否定句)

Mary ________ ________ Italian before．

5．Mr. Smith has few friends,________ ________?(完成反意疑问句)

视准轴垂直于横轴的检校目的是使视准轴垂直横轴,望远镜绕横轴纵转时,视准面是一个平面。