There are so many viruses on the Internet. If ____ accidentally, the viruses may make your computer break down.
My parents insisted that I _____ medicine instead of law.
________ was it that made the singer ______ his Asia Tour Concerts.
He ______ his sister to give up the plan for cycling along the Mekong River, but failed.
_______, the examination tomorrow has been cancelled (取消).
I have no money now. Even if I ______ money, I _______ such an expensive car.