单纯性机械性肠梗阻腹痛的原因是

A．梗阻部位以上肠管强烈蠕动

B．梗阻部位肠管坏死

C．梗阻部分以下肠管痉挛

D．炎症渗液刺激腹膜

E．腹腔内脏神经受到刺激

28．He spent much of the evening with Robert Green,____he had hardly seen in the thirty years since they had worked together at CBS.

A．what

B．that

C．who

D．Whom