针对建设工程的共性和地铁工程的特殊性,应把防______、防触电、防坠落、防火灾等作为安全工作的重点。
参考答案：坍塌
When _______ there, the postman found the door locked and then stopped _______ the letter in the mailbox on the wall.
A．reaching; putting
B．reached; to put
C．reaching; to put
D．reached; putting
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