There are many good stories about the Long March this is the most instructive.A. of which

问题补充：

There are many good stories about the Long March, this is the most instructive.

A. of which

B. in which

C. from which

D. by which

答案：

(答案→)A. of which

B. in which

C. from which

D. by which

解析：考察定语从句。本题定语从句的先行词是many good stories,后面的定语从句中句子结构很完整，故使用关系副词where，在定语从句中关系副词=介词+关系代词。本句是指在这些故事中，这是最有教育意义的。故使用of表示所属关系。故A正确。