_____for the free tickets, i would not have gone to the films so often

C ,对过去的情况的假设， 要不是 had句首， 句子倒桩

had it not been

因为
i would not have gone to the films so often
的would是过去的
，又因为前面的事发生较早，所以用过去完成时
had it not been

从i "would not have gone" to the films so often可看出考点为虚拟语气，并且是与过去的事实相反，答案只能是 had it not been

had it not been,
第一，先剔除不是过去式的也就是1．

再者，不能用they代表tickets，只能用it，所以4不行。

反正，答案是3。不知道怎么解释最后两个选择