此句的Which指代主语还是表语

August and Septemberare the months of the year, during which most English people take their holidays.

老师好，which指代主语August and September，还是指代表语the months of the year?还是皆可？

during which...这个定语从句是the months of the year的限制性定语，没这个定语从句，主句就失去了交流意义，等于在说废话。所以原句中的逗号为错误，需要删去逗号。