that young babies learn to do things because certain acts lead to awards.
| A．It is widely accepted |
| B．What is widely accepted |
| C．Which is widely accepted |
| D．That is widely accepted |
Only when you have finished your homework ______ go home.
| A．can you | B．would you | C．you will | D．you can |
It was in the street ______ I live that I met Mr. Green.
| A．that | B．which | C．where | D．when |
A man may usually be known by the books he reads _______ by the friends he keeps.
| A．as well as | B．as if | C．as soon as | D．as usual |
There are so many books! It is not easy for us to decide what to take and what to_______.
| A．take on | B．pick up | C．leave behind | D．work out |
When I try to understand _______ that prevents so many Americans from being as happy as one might expect, it seems to me that there are two causes.
| A．why it does | B．what it does | C．what it is | D．why it is |