For a linear regression, you should always do which of the following:
A. Use AIC to see if the R-squared value is large enough for your model
B. Use the p values and standard error of the intercept as well as the R-squared value to see if it's a good model
C. Look at the estimates and standard error of the slope to see if your model is working
D. Use the p value for the slope and the size of the R-squared value to see if it's a good model