chuyển sang câu bị động passive voice 30/nobody showed them their seats. 31/they have sold that old houses at the end of the road. 32/their teachers are making them learn hard this semester. 33/he couldn't repair the broken vase. 34/people say that he is a robber. 35/they couldn't do any thing to stop the fire. 36/people sold more newspapers during the election. 37/Sarah's parents gave her a computer on the occasion of her birthday. 38/they built this house last year. 39/nobody has cut the grass for weeks. 40/nobody knowns anything about Breeder's family. 42/people think that someone started the fire deliberately. 43/they haven't made a decision yet. 44/people say that Chris is in the army. 45/no one has signed the letter. 46/people think that one apple a day is good for health. giúp em với ạ