To what extent do you agree with the following statements?
a. The best test of the performance of two different regression equations is their respective values of R2.
b. Time-series regressions should be run using as many years of data as possible; more data means more reliable coefficient estimates.
c. Including additional variables (even if they lack individual significance) does no harm and might raise R2.
d. Equations that perform well in explaining past data are likely to generate accurate forecasts.