问题
选择题
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
答案
答案：B
B 考察定语从句。One theory is that…to chew是主句，________ suggested by Harvard University是非限制性定语从句，as在引导非限制性定语从句时候，有正如的意思，且通常表示被动。Which没有这个用法。故B正确。