Ans: C
Rewrite the equations of $L_1$ and $L_2$ as $L_1:~ y=-ax+b$ and $L_2:~ y=-cx+d$.
Rewrite the equations of $L_1$ and $L_2$ as $L_1:~ y=-ax+b$ and $L_2:~ y=-cx+d$.
I is true. According to the figure, the slope of $L_1$ is positive. Then we have $-a>0$. i.e. $a < 0$.
II is false. According to the figure, the slope of $L_2$ is greater than that of $L_1$. Then we have $-c > -a$. i.e. $a > c$.
III is true. According to the figure, the $y$ intercept of $L_1$ is greater than that of $L_2$. Then we have $b > d$.
IV is true. By the reasons of I, II and III, we have $a<0$, $a>c$ and $b>d$. Then we have $ab < cd$.
