people in the west make_ a rule to buy christmas presents for their relatives and friends .people in the west make it a rule to buy christmas presents for their relatives and friends .此处为何用it
问题描述：
people in the west make_ a rule to buy christmas presents for their relatives and friends .
people in the west make it a rule to buy christmas presents for their relatives and friends .
此处为何用it
答
it 是形式宾语，真正宾语是不定式短语 to buy christmas presents for their relatives and friends. 因为太长，所以放在句尾，而用It 放在句中代替。
答
it 作形式主语,真正的主语是后面的动词不定式.