答案：D

题目分析：考查代词，it是形式宾语，真正的宾语是后面的不定式to talk to him about anything serious，所以选D

点评：本题着重理解it作为代词时，为了避免“头重脚轻”可以将it置于句首作为形式主语，而其后的不定式或是从句作为真正的主语这种用法。例如：It is very important for you to understand how to pronounce the word.此外it也可以放在实意动词之后作形式宾语，用法同作主语时一样，像此题中的例子就是

即学即练：People in the west make_______ a rule to buy Christmas presents for their relatives and friends.  

A. it         B. that      C. this       D. as

选A