[单选题]
The length of time the shutterjt,25pgbz7 kt is open and the film is exposed:7 kuzjr .sg)57t yr1:azzp s;x) ckia in a camera is determinedy7 1g sz : :rjzuapiz75.xk;c )a)rtsk by the
A. shutter speed.
B. f-stop.
C. focusing.
D. none of the given answers
