The following is the list of MAD statistics for each of the models you have estimated from time-series data:

Model MAD
Linear Trend 1.38
Quadratic Trend 1.22
Exponential Trend 1.39
AR(2) 2.71

Based on the MAD criterion, the most appropriate model is:

A. linear trend.

B. quadratic trend.

C. exponential trend.

D. AR(2).