帮帮忙写下这些句子的被动语态、否定句 和疑问句
1/Every can understand his idea
2/You can buy computersquite cheaply now
3/We can speak a little English
4/You mustn't take these magazine from the library
5/She has already taken many phobs
6/Children should do their homework on time
7/Computers may replace books one day
8/We have heard the song before