Which statement about the working principle of the still camera is true?

A.
Light entering the camera through a nonadjustable opening is focused on light-sensitive film at the back of the camera.
B.
Light entering the camera through a light-sensitive opening is focused on 35mm film at the back of the camera.
C.
Changeable lenses of different focal lengths allow light to enter the camera, which then forms the image on light-sensitive film.