Nobody believes a 92-year-old could run a marathon_______she passed the finishing line. People of all ages can challenge themselves.

A. if B. since C. until

C

本题考查连词的用法。本题考查固定短语not…until直到……才……句式。句意：直到她通过终点线，没有人相信一个92岁的老人能够跑马拉松。各种年龄的人都可以挑战自己。