Recall the formula for finding the equation of a line is that given a point P(x1,y1) the equation of the line is
(y - y1) = m·(x - x1) where m is the slope and x1 and y1 are the coordinates of the given point , so you have:
m = ½, x1 = -2, and y1 = 1
Plugging in these numbers: (y - 1) = ½·(x - (-2)) = ½·(x + 2)
So (y - 1) = ½·(x + 2) looks just like answer D, but we can simplify further to get:
y = ½·x + 1 + 1 = ½·x + 2 which is answer A. So both A & D are correct.
Answer B is clearly wrong, since in its simplified form slope = -2 and b = 1/2 clearly don't match with A0.
What about answer C? If you rearrange: x = 2·y - 4 ⇒ ½·x = y - 2 ⇒ ½·x + 2 = y which is also = A)
So C is also a solution.