问题
选择题
Mark Twain worked for several years as a pilot on a steamboat, taking passengers up and
down the Mississippi, the great river ___flows from the north of the US near the Canadianborder.
A．as
B．what
C．which
D．who
答案
答案：C
题目分析：考查定语从句。Which指代先行词river在定语从句中做主语；故C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。