出铁口深度过深，且出铁时间长，则开口机钻头应改用（）。
参考答案：大直径钻头
We'll have a sports meet for the next three days.________, we won't have lessons for three days. [ ]
A. In other words
B. On the other hand
C. For one thing
D. As a matter of fact
地下储气库的定义是？
