1 The scientist has already written his article
2 Andrew's hamster has just eaten his food
3 The boys found an old cage in their garden
4 They haven't discussed the problem yet
5 Charles has just finished his translation
6 They went to the theater last week
7 My cousin has been to the theater three times week
8 His niece has just written the invitation letters
9 Helen came home, had a short rest, and then began to help her
10. ....your relatives took part in demonstration yesterday