例:He ordered that every one ________when the enemy was approaching.a keeps silent b. kept silent c. must be silent d.keep silent我觉得选最后一个,不知对不对?好几年没学外语了,现在再拿起来有点忘了不少。还有一个问题是,我记得有一些动词,它们引导的宾语从句中,动词应该用原型的,请列举。谢谢。