关于虚拟语气的问题the professor recommended that everyone_____(refer
关于虚拟语气的问题
the professor recommended that everyone_____(refer to)this paper.
Al`s doctor insists that he_____(rest)for a couple of days.
这个两个填空从书上摘的,它们的答案都是没有should的原形,既refer to 和rest,我想问,should能不能加,及其原因.
补充说明,书上其他答案都是(should)+动词原形,惟独这两个没有should,而是直接用动词原形,请明白的帮忙解释下,谢谢.