This study website is really helpful, _____middle school students and parents can benefit a lot.[ ]

A. which                    

B. why          

C. from which                

D. of  which    

慢性胃炎的主要致病因素是（）

A.细菌毒素或微生物感染

B.酗酒和暴饮暴食

C.精神神经功能障碍

D.长期服用某些药物

E.幽门螺杆菌感染