1.sometime:过去或未来的一个时间点 可用于一般过去时与将来时.例如：You can hand in your homework sometime before Friday.你可以在周五前某个时候交作业.some time：一段时间 大多数是完成,将来,跟在for后面 som...那么the number of the students studies hard和a number of students study hard有什么区别？ 照你说改被动语态的能否改为i am let to play computer by my mother once a week1the number of the students studies hard中the number作为主语 三单 所以要用studiesa number of students study hard中students作为主语复数，所以用study2不能 let没有被动语态改为被动语态需要换其他单词 可以看3last have wish let take part in break out happen没有被动语态改为被动语态需要换其他单词My mother let me play computer once a week.变被动语态是l was allowed my mother to play computer once a week。 let换成了allow明白了么······let不是使役动词吗？我记得老师讲过还原to