. My study of biology has ___C___ much of my spare time， but it has given me a great deal of enjoyment.
| A．taken off | B．taken down | C．taken up | D．taken away |
The boys followed the marks that they ______, until finally they found their way back to the campsite.
| A．left | B．have left |
| C．had left | D．have been left |
He won’t apologize to us ______he is wrong.
| A．as if | B．in case |
| C．since | D．even though |
__________the truth, we’re sure she won’t tell a lie.
| A．Whichever | B．Whatever |
| C．Whenever | D．However |
Mr. Baker including some tourists ______ the Great Wall before, so they headed for the Forbidden City.
| A．has gone to | B．have gone to |
| C．has been to | D．have been to |
One reason why he succeeds is ______he is good at thinking in different ways.
| A．because | B．as | C．which | D．that |