During the days ______, he made great progress in learning English.         [ ]

A. following

B. followed

C. to follow

D. that followed

术后切口感染的原因是

A．备皮不符合要求

B．手术时组织损伤多，止血不全

C．术后严重腹胀

D．术前常规使用抗生素

E．无菌操作不严