对于赛场发生的球迷闹事，应及时（）。
A、不予理睬
B、听之任之
C、予以制止
D、观其动态
参考答案：C
-People find it hard to get across the river.
-I think at least two bridges over it. [ ]
A. need
B. are needing
C. will need
D. are needed
在一棵二叉树上第8层的结点数最多是______。
A．8
B．16
C．128
D．256
