Changing the 1-pin row into the 4-pin row requires all 3 moves. There are no moves left to complete the solution of the problem.

Changing the 3-pin row into the 4-pin row would require moving the 3 pins above the 3-pin row, plus one of the pins at either end of the 4-pin row. That is more than 3 moves.

Since neither the 1-pin nor the 3-pin row can become the 4-pin row, it must be that the 2-pin row will become the 4-pin row.