She is a teacher of________ .

She is a teacher of________ .
A、20 year’s experiences
B、20 year experiences
C、20 years’ experience
D、20 year experience
【正确答案】：C
【题目解析】：experience意为“经验”，是不可数名词，没有复数形式；“二十年的经验”应表述为20 years’ experience。