I _____ you up at eight but you didn’t answer.—I ____ in the kitchen then．

Getting to other planets or to themoon _____ many problems

ened to Dr．Wilson’slecture about the protection of wild animals, but I was unable to grasp its key.

It is reported that the scientists in our county are______all possible ways to control H1N1 flu.

The workers are all tired, but ________ of them stopped ________ a rest.