[单选题]
The length of time the shutter is openqtcukl /2)/al +fcaf1py.ybg9y ab-7 and the fidt :ipl4)n;y5yoz6 t t08 twtilm is exposed in a camera is determi5tttt;pndywii: lz8 )y 4o0 t6ned by the
A. shutter speed.
B. f-stop.
C. focusing.
D. none of the given answers
