It's wrong___not___him a letter.A:of me ;to write B:for me ;to write

选A正确!
考点：
固定句型 It+ be+adj+of/for sb to do sth 中的形容词与介词搭配.
当形容词表示主语的【品质、特点、属性等】,用of;
当形容词修饰不定式短语时,用for.例如：
It is nice /kind of you to say so
=You are nice/kind to say so
It is important for us to learn a foreign language.
所给句子意思是：
我错了没有给他写信.
所以,应该表达为：
It is wrong of me not to write him a letter.