------ Can I help you?
-------- No, thank you. I __________ now.
| A．have been served | B．have served | C．am being served | D．am serving |
Swan Lake is a famous ballet(芭蕾) in four acts, ________ on a German fairy tale.
| A．basing | B．based | C．bases | D．to base |
He had no idea of how the climb would be _______ he was half way up the mountain.
| A．when | B．until | C．while | D．as |
—Would you like some more chicken?
—No, thanks. I am ______ a diet and try to ______weight.
| A．on; lose | B．on; put on | C．in; have | D．in; lose |
. Alien had to call a taxi because the box was _____ to carry all the way home.
| A．much too heavy | B．too much heavy |
| C．heavy too much | D．too heavy much |
___ more and more forests destroyed, some animals are facing the danger of dying out.
| A．As | B．By | C．For | D．With |