1 . One of the most __________ (strike) features of Beijing Opera is that the performers often sing with very high voices. (所给词的适当形式填空)

2 . Up to now lots of tests ________ (prove) that the system works.   (所给词的适当形式填空)

3 . My washing machine ________ (repair) this week, so I have to wash my clothes by hand. (所给词的适当形式填空)

4 . We need to take steps to save endangered species, including setting up special zones ________ plants and animals can be protected. (用适当的词填空)

5 . After the heavy rain, the ground got so wet, ________ caused a lot of road accidents. (用适当的词填空)

6 . ________ worried me that my mother’s eyesight was declining. (用适当的词填空)

7 . We ________ (wait) for him for over an hour when he finally turned up at the meeting. (所给词的适当形式填空)

8 . Sam ________ (write) the novel for three years and it was published last week. (所给词的适当形式填空)

9 . What a nice day today! Do you feel like ________ (go) for a picnic? (所给词的适当形式填空)

10 . It is a big challenge ______ (find) and keep the right balance between progress and the protection of cultural sites. (所给词的适当形式填空)