By the time she is 50 years old, she ______ an inmate of the prison for over half of ______ her life.
【正确答案】 C
【答案解析】解析：本题的考点是由介词by所引导的将来时间短语所决定的将来完成时态。当一个句子中出现介词by所引导的将来时间短语时，主句的时态应该用将来完成时态(will have done)。