I don’t think one can keep healthy ______ taking enough exercise.[ ]

Some of the students are afraid of the teachersstrict with them.

Hello, mum. Are you still on Lushan Mountain?－Oh, no. We are back home. We _________ a really good journey.

I’m a little nervous to give an English speech this afternoon. —Come on ! Believe in ________ and you can do it.

Children under sixteen are not permitted to participate in such kind of activities _____ bad for their mental development.