国家开放大学 / 综合英语（2）
正确率：100%
I have turned the house _ _ _ _ _ _ looking for my keys, but I failed.
a. up-to-down
b.upside down
c.up and down
d.upside to down
a. up-to-down
b.upside down
c.up and down
d.upside to down
参考答案：