Answer:
D
Explanation:
We need to understand the meaning of slope. The slope means the rate of change of y with every unit change of x.
In our case, it will be rate of change of sales increase (%) with respect to unit change of discount(%).
The formula for slope is the change in y divided by change in x.
From the 2 points given, we can say that slope is:

This means "as discount increases 1%, sales increase by 3%". Option D is right.