A warm thought suddenly came to me I might substitute the hero to buy some flowers for hi

问题补充：

A warm thought suddenly came to me I might substitute the hero to buy some flowers for his mother’s 60th birthday.

A. if

B. when

C. that

D. which

答案：

A. if

B. when

C. that

D. which

解析：考查名词性从句。that引导同位语从句，进一步解释名词thought。因为本句谓语部分短小，因此把从句放到了谓语部分的后面，形成分隔同位语从句，that在从句中不充当句子成分。