Traditional Culture Encyclopedia - Photography major - Photography five people

Photography five people

Knowing from the meaning of the question that this problem is a step-by-step counting problem,

First, two people were selected from the nine people in the back row, and there were C 9 2 kinds of results.

Then arrange two people in one of the seven positions, with a 7 2,

∴ Different adjustment methods are C 9 2 A 7 2,

So choose C.