潜水及潜水面的概念是什么？
参考答案：
潜水：第一个隔水层上含水层里具有自由表面的重力水。
潜水面：潜水的自由表面。
They were all out _________ the missing child.
A．found
B．to look for
C．find out
D．to look after
You’d better cut your hair short. Our school doesn’t __________ long hair.
A．approve of students wearing
B．approve students to wear
C．approve students wearing
D．approve of students to wear
