Not everyone has realized what_______ important part the balance of________ nature plays in their life.
| A．an；the | B．/；the | C．an；/ | D．the；/ |
．______two articles to write today，I have to stay at the classroom to make it.
| A．With | B．For | C．Because of | D．As for |
----_____is it that is troubling Mary ?
----Working out the maths problem..
| A．What | B．How | C．Why | D．Which |
I wonder how long it will take you_____ such a hard task within so little time.
| A．complete | B．to complete | C．completing | D．completed |
Tom was absent from school this morning, because sometimes he was a little weak and could ______ill .
| A．take | B．set | C．catch | D．fall |
. Will you pass me the dictionary _____ the cover is dark blue?
| A．its | B．which | C．whose | D．of which |