在梯子上工作应注意什么？
参考答案：
在梯子上工作时，梯与地面的斜度角为60°左右。工作人员必须登在距梯顶1m的梯蹬上工作。
_____ under the tree? No, they aren't. [ ]
A. Where are
B. What is
C. Are they
D. Is it
What _________ weather it is!
A．a terrible
B．terrible
C．rain
D．a rain
the tree? No, they aren't. [ ]