用所给词的适当形式填空。
My mother’s _______(hobby) are collecting stamps and listening to music.
The computer is _______(useful) than the radio.
Doing morning exercises is a good way to keep _______ (health).
—Where is your mother, Beibei?
—She is busy _______ (answer) the telephone.
Hobbies help people relax after their _______ (day) work.