某同学研究定滑轮的使用特点，他每次都匀速提起钩码，研究过程如图所示，请仔细观察图中的操作和测量结果，然后归纳得出初步结论。

比较(a)、(b)两图可知：____。

比较(b)、(c)、(d)三图可知：____。

Nancy：Hi，David．Welcome to my home．

David：Wow，____

Nancy：Thank you．

David：Is this your family photo?

Nancy：Yes．This is my mother．

David：Wow，she looks young．____

Nancy：She is a secretary．

David：Is your father a scientist?

Nancy：Yes，he works at a university．

David：____By car?

Nancy：No，he goes to work by bike．____

David：Great．He has a very healthy life．Look at your sister．____

Nancy：Yes,her favourite toy was lost．David,come to my bedroom．Let's play computer

David：Great

A．What does she do?

B．Your home is big and beautiful．

C．She looks worried．

D．How does he go to work?

E．He likes riding a bike．

如图所示电路中，如果要让A和B两盏灯组成并联电路，则开关的开、闭情况是（  ）