Spielberg, _____ mother was a musical teacher, was born in 1964 in a small town in America.

A．whose

B．who

C．that

D．whom

设函数f(x)在[0，3]上连续，在(0，3)内可导，且f(0)+f(1)+f(2)=3，f(3)=1，试证必存在ξ∈(0，3)，使f’(ξ)=0。