Answer
Choices (D) and (B) are correct.
Work Step by Step
To calculate the slope between points $(x_1,y_1)$ and $(x_2,y_2)$, we use the formula:
$slope=m=\frac{y_2-y_1}{x_2-x_1}$
This definition matches (D). The answer is (B) is reversed, but this yields the same result:
$slope=m=\frac{y_1-y_2}{x_1-x_2}=\frac{-(y_2-y_1)}{-(x_2-x_1)}=\frac{y_2-y_1}{x_2-x_1}$
So choices (D) and (B) are correct. (A) has the subscripts mismatched, while (C) has x and y mismatched.
