补全对话。

Peter: Oh, David. Please don't put anything on this desk!

David: 1_____?

Peter: Look! This leg is broken.

David: 2_____. When did you find it?

Peter: I found it just now when I was sweeping the floor.

David: Let's tell our teacher about it at once and then someone will repair it.

Peter: No. 3_____.

David: Yourself? Have you learnt to repair a desk?

Peter: Yes. My father is an expert in repairing things. 4_____.

David: Oh, your father taught you. That's great! Do you think 5_____ ourselves?

Peter: Certainly. Let's begin.

门窗放置时不应直接接触地面，下部应放置垫木，门窗与地面所成角度不应小于（）o，并应采取防倾倒措施

A.50

B.60

C.70

D.80