问题补充：
for the free tickets, I would not have gone to the films so often.
A. If it is not
B. Were it not
C. Had it not been
D. If it were not
答案：
A. If it is not
B. Were it not
(答案→)C. Had it not been
D. If it were not
解析：考查虚拟语气。if虚拟条件句常把if省略，把were，had，should提到句首。对现在虚拟，if从句用一般过去时，be动词用were，主句用would do sth；对过去虚拟，if从句用过去完成时，主句用would/could ahve done sth；对将来虚拟，if从句用过去时/ were to/should+动词原形，主句用would do sth。根据主句would not have gone to可知，这里是对过去进行虚拟，if从句用had done，故选C。
