问题
选择题
Lawrence Craven, a doctor from the USA, is the author of several published reports, one of ________ introduced the idea in 1953 _________ aspirin could reduce the risk of heart attacks.
A．them; when
B．which; that
C．what; that
D．which; when
答案
答案：B
题目分析：考查定语从句。本定语从句的先行词是reports，which指代reports作为of的宾语。第二空的定语从句先行词是1953，本定语从句结构很完整，所以使用关系副词when。故B正确。
点评：定语从句的关键在于分析句子成分，如果句子很完整就使用冠词副词；如果句子中缺少主语，宾语，表语或者定语则使用关系代词。