已知二维随机变量 $(X, Y)$ 的分布函数为 $F(x, y)=A\left(B+\arctan \frac{x}{2}\right)\left(C+\arctan \frac{y}{3}\right)$, 则
A
$A=\frac{1}{\pi^2}, B=\frac{\pi}{4}, C=\frac{\pi}{6}$
B
$A=\frac{1}{\pi^2}, B=C=\frac{\pi}{2}$
C
$A=1, B=\frac{\pi}{4}, C=\frac{\pi}{6}$
D
$A=1, B=C=\frac{\pi}{2}$
E
F