The atmosphere of the earth ______ us from the strong sun light.
| A．prevents | B．keeps | C．stops | D．protects |
This is the _________ spot on which the first pilgrims landed in America.
| A．historic | B．natural | C．historical | D．traditional |
After retiring, he was recommended to ____ gardening as a hobby．
| A．take up | B．take on | C．take off | D．take away |
I ________ thank you too much for all your help to my son while we were away from home.
| A．won’t | B．can | C．can’t | D．will |
. I'd really appreciate ________ if you would turn off the lights before you leave.
| A．you | B．that | C．as | D．it |
It never _____ humans until the mid1990s that some animals can be cloned.
| A．occur | B．is occurred | C．occurred to | D．occurred |