【练习】根据句子结构，用括号内所提供词的适当形式填空
1) They encouraged the _______ to _______ in the singing performance after the contest..(participate)
2) The doctor are ________ on an ______ of a factory who got injured when _______a machine, and the ________ is said to last over ten hours.(operate)
3) The seats in the plane are ________ , and you can ________ them to a certain angle. The ______ is not difficult to make. (adjust)
4) The drinks were ________ to them by coca cola company and they received _______from other companies as well. (donate)
