先令x+1=0,则-1f(0)=0,所以f(0)=0;再令x+1=1/2,则-1/2f(1/2)=1/2f(-1/2),则f(1/2)=f(-1/2),因为f(x)在R上是偶函数，则f(-1/2)=f(1/2)=0,以此类推，f(5/2)=0.所以f(f(5/2))=0,选A
B
