After visiting China，most of the foreign friends said they would never forget the time they had spent in China.
A. that
B. what
C. when
D. at which
网友回答
(答案→)A. that
B. what
C. when
D. at which
解析：考查定语从句，先行词是the time，定语从句中spend是及物动词，缺少宾语，用that引导定语从句，句意：到过中国后，很多外国人说他们永远忘不了在中国度过的时光。选A。