Which one of the following statements is true?

a.

None of the suggested answers are correct.

b.

When an additional explanatory variable is introduced into a multiple regression model, the coefficient of multiple determination will moderately decrease.

c.

When an explanatory variable is dropped from a multiple regression model, the coefficient of multiple determination can increase.

d.

When an additional explanatory variable is introduced into a multiple regression model, the adjusted r² can never decrease.

e.

When an explanatory variable is dropped from a multiple regression model, the adjusted r² can increase.