1We should keep the food at a low temperature.被动语态 The food should ------- ------ at a low temperature.2.How long did it take you to do your homework yesterday evening?改为同义句 How long did you---- ---- your homework yesterday evening?3、He gave me no chance to answer his question.改为同义句He didn't give me a chance to ---- ----- his question .4、I have to be back by 5:00pm对划线部分提问.----- ----- you have to be back