Many people were in favor of the proposal that a special committee________to investigate the incident.
句意：许多人同意他的提议，应该成立一个特别委员会调查此事。proposal后面的同位语从句中的谓语动词应该用should+动词原形形式的虚拟语气。committee与 set up之间为被动关系，故应该选C。