A (Aperture Priority)
Explanation: Aperture priority means that you choose an aperture (f-stop) and the D7000 will choose a corresponding exposure time.
The aperture can be selected with the sub-command dial at the front.
Tips: This is an alternative to mode P for easy choice of a specific aperture.
But you can get the same results in mode P and especially the recommended modes U1 and U2 by turning the command dial at the back to shift the combination of aperture and exposure time.