"should" 是一个情态动词，后面应该接动词的原形。例如：
1. You should eat more fruits and vegetables.
2. They should be here by now.
3. This should help you relax.
4. You shouldn't smoke so much.
5. We should respect each other's privacy.
"should" 之后接动词原形，没有人称和数的变化。它用于表达建议、责任、义务或预期等概念。在否定句中，"should" 后面则接 "not" 加上动词原形，缩写为 "shouldn't"，表示“不应该”。例如：
1. You shouldn't be late for the meeting.
2. They shouldn't ignore the warning signs.
此外，"should" 还可以用于虚拟语气中，通常用于表示与现在事实相反或将来成为现实的可能性很小的情况。例如：
1. If I had known you were in town, I should have called you.
2. She should have finished her homework by now.
综上所述，"should" 后面应该接动词原形，用于构成谓语，表达建议、责任、义务或预期等概念。在否定句中，则接 "not" 加上动词原形。在虚拟语气中，"should" 通常用于表示与现在事实相反的情况。