1 . When asked to explain       he did to make his students so fascinated with his lessons the teacher paused and thought deeply.

A．what it was that	B．that what it was
C．what was it that	D．that what was it

2 . Can you explain ________ the sun goes down in the west?

A．why is it that

B．why it is that

C．how it is that

D．how is it that