[求助]GWD3 一道排列组合题

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

The answer goes to A.

123/456   124/356 125/346 134/256 135/246