Nowadays for many people a winter vacation simply doesn’t count           it includes several days in the ski run.

A．unless            B．until     C．once          D．though

Nowadays for many people a winter vacation simply doesn’t count ______ it includes several days on the ski run.

　 A. unless　　　　　　 B. until　　　　　　 C. once　　　　　　 D. though