A lot of people don’t learn from their mistakes they get hurt. A. whetherB. whenC. ifD. u

问题补充：

A lot of people don’t learn from their mistakes they get hurt.

A. whether

B. when

C. if

D. unless

答案：

A. whether

B. when

C. if

(答案→)D. unless

解析：句意：许多人直到他们受伤了，他们才会错误中吸收教训。Whether是否；when当……时候； C. if 如果； unless除非，直到……才。根据句意故选D。