Your version of D is different from the picture y = 1/4 x + 6
However steepness is not related to the sign of the coefficient of x!
In your four options A and D both have a steepness of 1:1 (45 degrees of slope). One slopes up and the other down.
In the original question D has a slope of 1:4 which is much smaller than B which is 7:1
