Find the Slope Then Describe What It Means in Terms

Find the slope then describe what it means in terms of the rate of change of the dependent variable per unit change in the independent variable.
-The linear function f(x) = -5.3x + 21 models the percentage of people, f(x) , who eat at fast food restaurants each week x years after 1998.

A) m = 5.3; the percentage of people eating at fast food restaurants each week has increased at a rate of 5.3% per year after 1998.
B) m = 21; the percentage of people eating at fast food restaurants each week has increased at a rate of -5.3% per year after 1998.
C) m = 5.3; the percentage of people eating at fast food restaurants each week has increased at a rate of -5.3% per year after 1998.
D) m = -5.3; the percentage of people eating at fast food restaurants each week has decreased at a rate of -5.3% per year after 1998.