什么是干式变压器？
参考答案：
变压器的铁芯和绕组（线圈）都不浸在任何绝缘液体中的变压器称为干式变压器。
When I returned to my study, I found the floor thoroughly _____ and all my books _____ according to the types of books.[ ]
A. cleaning; ranging
B. cleaned; ranged
C. have cleaned; ranged
D. has cleaned; ranged
