True or false:
a. For any set of data, there is always one best model.
b. When there is no physical theory to specify a model, there is usually no best model, but many that are about equally good.
c. Model selection methods such as best subsets and stepwise regression, when properly used, are scientifically designed to find the best available model.
d. Model selection methods such as best subsets and stepwise regression, when properly used, can suggest models that fit the data well.