Consider bootstrap aggregation, or bagging, of a regression tree. Which of the following statements about bagging in this context is true?

a) Bagging tends to increase mean squared prediction error by reducing bias while keeping variance unchanged. b) Bagging tends to increase mean squared prediction error by reducing variance while keeping bias unchanged.

c) Bagging tends to decrease mean squared prediction error by reducing bias while keeping variance unchanged.

d) Bagging tends to decrease mean squared prediction error by reducing variance while keeping bias unchanged.