托盘的操作要求是什么？
参考答案：
平、稳、松。
简述有底柱分段崩落法的主要优缺点。
—Do you think it will do us good or harm?
— ________. Let's beg for God's help. [ ]
A. It's hard to say
B. I'm sure
C. It's impossible
D. You are right
