If I ______ work harder at school, I would be sitting in a comfortable office now.
worked B. were to work C. had worked D. were working
针对此题，根据题干中“ I ______ work harder at school（在学校学习更努力的话）”和“sitting in a comfortable office now（现在就会在舒服的办公室里坐着）”可知，从句中的“at school”相对主句中的“now”而言为过去的情况，根据if虚拟语气的语法规则，可知正确答案为选项C。
