Mary plays light music _________ her free time to enjoy the beauty of music.
in
at
on
I have two books. One is for you, ________ is for her.
Mr. Li is kind _________ us. But sometimes he is kind _______ serious.
Please help me _____ English.
It’s 8 o’clock. The students _________ an English class.
--- Don’t run in the hallways. --- ______, I won’t do it again.