Brent is trying to figure out the relationship between the number of times his friends post on social media and their grade point averages. He records the collected data on a scatter plot. Which of the linear functions best models the line of best fit? What does the slope in the equation represent?

A)
y = 0.004x - 4; the average number of posts per friend

B)
y = -0.5x - 4; the amount of decrease in the GPA for each post

C)
y = 0.05x - 4; the amount of increase in the GPA for each post

D)
y = -0.004x + 4; the amount of decrease in the GPA for each post