1. 主动语态与被动语态相互转换，每空一词（含缩写）。
56. We call maths the language of science. （改为被动句）
Maths _________ _________ the language of science.
57. Where did they plant trees? （改为被动句）
Where _________ trees _________?
58. You can borrow two books at a time.（改为被动句）
Two books _________ _________ _________ at a time.
59.The teacher made the students copy the text.改为被动句
The students _________ _________ _________ copy the text.
60. They produce silk in Suzhou.（改为被动句）
Silk _________ _________ in Suzhou.
61. They built a bridge between the two islands last year. （改为被动句）
A bridge ________ ________ between the two islands last year.
62. A birthday party will be given tomorrow. （改为主动句）
We _________ _________ a birthday party tomorrow.