【定义】主谓一致即主语和谓语在人称和数上必须保持一致。
一、意义(语法)一致原则
只要确定句子的主语是单数意义，则谓语单数，句子的主语意义复数，则谓语复数。
【完成句子】
用动词的适当形式填空
(1) Physics is (be) not easy to understand.
(2) When and where to go for the on－salary holiday has (have) not been decided yet.
(3) Either of the stories is (be) very funny.
(4) Nothing is (be) impossible.
