问题补充：
Lawrence Craven, a doctor from the USA, is the author of several published reports, one of which introduced the idea in 1953 aspirin could reduce the risk of heart attacks by thinning blood.
A. when
B. where
C. that
D. which
答案：
A. when
B. where
(答案→)C. that
D. which
解析：考查同位语从句：Lawrence Craven,一个来自美国的医生也是几个发表的报道的作家，其中之一介绍了1953年的想法，阿司匹林可以通过使血液稀薄来减轻心脏病的危险。所以这是同位语从句，同位词是idea，that连接的从句对idea的内容进行说明。选C。
