全断面中风化岩层盾构掘进一般采用()的模式。
A、土压平衡模式
B、空仓推进
C、半气压
D、土压欠压
参考答案:B
There are two thousand students in this college, ______ are from the countryside.
A.one-third of them
B.one-third of which
C.one-third of whom
D.one-third in which
根据问题的清晰性分类,研究性学习中涉及的问题多属于 问题。