Pauley graphs the change in temperature of a glass of hot tea over time. He sees that the function appears to decrease quickly at first, then decrease more slowly as time passes. Which best describes this function?

It is linear because the graph decreases over time.

It is linear because there is both an independent and a dependent variable.

It is nonlinear because linear functions are increasing functions.

It is nonlinear because linear functions increase or decrease at the same rate.

"It is nonlinear because linear functions increase or decrease at the same rate."

Step-by-step explanation:

Linear function decrease/increase at a constant rate.

If we need variables increase/decrease, then we choose a non-linear function.

According to Pauley, the function [temperature] decreases at a higher rate at first and then decreases at a lower rate eventually. So there is change in rate. So, we can describe this graph as non-linear. Because linear functions increase or decrease at the same rate, which here is non-applicable.

Thus, the 4th option is right, "It is nonlinear because linear functions increase or decrease at the same rate."

Answer: D