Jorge was tracking the decreasing temperature in the morning. At 7 a.m., it was 65 degrees Fahrenheit. At 9 a.m., it was 55 degrees Fahrenheit. If Jorge made the function f(x) = −5x + 100, what would the −5 represent?

AThe temperature at midnight

BThe length of time he recorded for

CThe total change in degrees

DThe rate at which the temperature was decreasing