It was my sister first had the idea to cycle along the river.
A. which
B. what
C. /
D. who
网友回答
A. which
B. what
C. /
(答案→)D. who
解析：考查强调句型；强调句型的基本结构：It is/was被强调成分that/who其它成分；强调句型的最大特点是把it is/was…that/who…去掉，句子仍然成立。本题强调的是my sister，指人，所以可以是who也可以是that，句意：正是我的姐姐第一个想起了沿着河边骑车的主意。故D正确。