单项选择题
设4/(1-x2)·f(x)=d/dx[f(x)]2,且f(0)=0,则f(x)等于:()
A.(1+x)/(1-x)+c B.(1-x)/(1+x)+c C.1n|(1+x)/(1-x)|+c D.1n|(1-x)/(1+x)|+c
A.ln|1+f(x)|f+c B.(1/2)1n|1+f2(x)|+c C.arctanf(x)+c D.(1/2)arctanf(x)+c
A.-36 B.12 C.36 D.以上都不对