下列不属于流体的是（）。
A.水
B.固体硫磺
C.空气
D.液体硫磺
参考答案：B
It was _________ that everyone like to read it.
A．a so interesting story
B．so an interesting story
C．a story so interesting
D．so interesting a story
设平衡的二叉排序树(AVL树)的结点个数为n，则其平均拉索长度为
A．O(1)
B．O(log2
C．O(
D．O(nlog2
