用括号中所给动词的适当形式填空，使句子表达更准确。
1．They want people______________（not kill）pandas．
2．____________she________________（visit）China before?
3．I tried________________（understand）the poems．
4．－When_________ the plane________________（take off）from Beijing
Capital Airport?
－Next Sunday．
5．They made the reserves_____________（help）pandas．
6．Astronauts____________（be）to the moon and returned safely．
7．－How long_____________ you__________（study）English?
－For two years．
8．It’s a good idea___________（bring）an umbrella．
9．What__________ you _________at ten o’clock last night?
10．you mustn’t_________________（eat）in the library．
1．not to kill 2．Has，visited 3．to understand 4．will，take off 5．to help
6．have been 7．have，studied 8．to bring 9．were，doing 10．eat