1.Keeping a pet is not an easy thing.(改为同义句） Keeping a pet can____ _____
2.我到处找我的书,但我找不到.I ___ ____my book______,but i can't____ it.
3.我们永远不知道未来会发生什么.We’ll___ know what ___ ___ in the future.
4,电脑如今被人们广泛地使用.The computer ____ widely ___ ____people today.