What color_____ the cats?—I think ________white and black.

Mum is ill in bed now. I must ____________ her.

I have a lot of problems ______ physics.[ ]

What would you do, _____ if you saw someone stealing? [ ]

It has been written into law that drink driving can be a crime(罪).—I quite agree. We should better be careful not to _____________the law.