男性，30岁，上腹疼痛伴反酸3年，昨日始呕血，黑便总量约400ml，最大可能出血的原因是

A．应激性溃疡出血

B．胆道出血

C．胃癌出血

D．胃十二指肠溃疡出血

E．食管胃底静脉曲张破裂出血

They are said______each other long time before they met in Harvard University where they worked together on a research project.

A．to know

B．to have known

C．knowing

D．having known