One theory, ________ suggested by Harvard University, is that humans began cooking their food, thereby releasing nutrients locked in the raw food and reducing the time needed to chew it.

A．which

B．as

C．that

D．what

孕29周患者出现无痛性无诱因 * * 出血5天，超声检查见胎盘覆盖于子宫颈内口，该孕妇考虑为（）。

A.胎盘早剥

B.部分性前置胎盘

C.边缘性前置胎盘

D.低置胎盘

E.中央性前置胎盘