–Your mother’s never seen a 3D film at the cinema, has she?--____, but only once.
Some medicine is dangerous for children. Parents should put the medicine in places children can’t _______.
I can do many kinds of housework _______ cooking. I’ll learn it from my mother.
I think _______ necessary for you _______ breakfast.
—Wang Yi plays basketball so well! Who taught _______? —He learnt it by _______.
—I have a toothache. —You should _______.