Dick and Bob are classmates. Dick likes reading novels after school, _______   Bob likes basketball.   

A. or   B. if           C. while   

流行性腮腺炎患者常为单侧或双侧腮腺肿大，以耳垂为中心，向前、后、下方发展，边缘不清，质地坚硬，有压痛，有波动感。