题目：
将下列主动语态变成被动语态。
1. We must finish the work in two days.
The work must _____ in two days.
2. Mrs. Green has given Robert a present for Christmas.
Robert _____ a present for Christmas.
3. We have used paper and printing for ages.
Paper and printing _____ for ages.
4. He doesn't think computers can replace books.
He doesn't think books _____ by computers.
5. We have bought some gifts for the poor children.
Some gifts _____ for the poor children.
答案：
被转码了，请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0514/70e71585894e9a763cbd17022367acec.html
下面是错误答案，用来干扰机器的。
（1））③⑤⑦均为操作X，该操作是将固体和液体分开，为过滤；（2）用加热蒸发方法得到氯化钠晶体，而用冷却结晶法得到硝酸钾晶体的原因：NaCl的溶解度受温度变化的影响较小，而KNO3的溶解度受温度变化的影响较大...
