(121)设∫f(x)dx=2cos(x/2)+C，则f(x)=()

(121)设∫f(x)dx=2cos(x/2)+C，则f(x)=()
A、sin(x/2)
B、-sin(x/2)
C、(1/2)cos(x/2)
D、-(1/2)cos(x/2)
【正确答案】：B