用unless代替下例句中的if…not:
1.     The flight will take off if it doesn’t rain heavily tomorrow.
2.     The passenger wants to change to another flight if there is no place on the flight.
3.     The customers will complain if we don’t change it immediately.
4.     George knows that he cannot become a pilot if he has no flying license.
5.     The hijacker will be ferocious（残忍的）if we don’t do as he tells us to.
6.     Jane won’t contact with you if she doesn’t have your address and telephone number.
 
 
参考答案:
1.    The flight will take off unless it rains heavily tomorrow.
2.    The passenger wants to change to another flight unless there is place on the flight.
3.    The customers will complain unless we change it immediately.
4.    George knows that he cannot become a pilot unless he has flying license.
5.    The hijacker will be ferocious（残忍的）unless we do as he tells us to.
6.    Jane won’t contact with you unless she has your address and telephone number.