He is practicing every day, preparation for the ice-skating championship.[ ]

Did you talk back to your mother when you were a child—Yes. But now I realize I was wrong. I really regret ___________that silly thing to my mum.

I don’t like math _______it’s difficult for me.

What is Mr Zhang doing—He is writing some English words ______ the blackboard ______ chalk.

Cycling isn’t _________ climbing, but both of them are interesting.