In order to make students have a good knowledge of science subjects, they are encouraged to______ their own science experiments.

A．operate

B．direct

C．manage

D．conduct

因溃疡病行胃部分切除术后直8个月，3个月前出现上腹痛，比术前更剧烈，并且偶排黑便，最可能的诊断是

A．碱性反流性胃炎

B．吻合口溃疡

C．残胃溃疡

D．残胃癌

E．残胃十二指肠溃疡