k值

扩展方向

[−1, 1], $F_x\ge 0$

A

(1, +∞) ∪ (−∞, −1), $F_y\ge 0$

B

[−1, 1], $F_x<0$

C

(1, +∞) ∪ (−∞, −1), $F_y<0$

D