China is a land of bicycles. At least it was back in 1992 when I traveled the country. Back then everyone seemed to be riding a bicycle. Millions of them, all black. Cars were rare. Yet since my arr
He had just lost his job when, at the precise moment, his girlfriend broke up with him. She ____ salt into his wound. A. rubbed B. had rubbed C. would rub
，
是方程
的两个根，则
=__________．