tt-33

Q33:

A photographer
            will arrange 6 people of 6 different heights for photograph by placing them in two rows of three so that each person in the first row is standing in front of someone in the second row.  The heights of the people within each row must increase from left to right, and each person in the second row must be taller than the person standing in front of him or her.  How many such arrangements of the 6 people are possible?

A.     5

B.     6

C.     9

D.     24

E.      36

为什么是5，我怎么算出来是6，我的想法是这样的，先排上最特殊的位置——最高最矮的各一个，然后是C（4，2），得到6，怎么不对，没有帖子