以下文段中，请判断各个句子分别是前提、中间结论还是主结论。 前提选P，中间结论选IC，主结论选MC
Obviously, fewer sessions of gym class lead to reduced fitness. ___ Last year, when students participated in gym class on a daily basis, 85% of the school's students passed the exam. ___This year, students had gym class twice weekly, and only 70% of them passed the test. ___ The cutback in physical education is seemly the primary contributing factor to K High School's increasing failure rate on the year-end physical fitness examination. ___