A正确用法应该是MINE我的（物主代词,所有物）,B正确用法应该是YOURS,剩余C和D徘徊.
C,I think Sally's bike is older than his,我想SALLY的自行车比他的旧；D,think Sally's bike is older than her,我想,SALLY的自行车比她还大（指岁月）.不知道C和D哪个才是出题人想要的答案.