因为late为形容词,用be动词修饰be + 形容词,也可以be + 动词ing表进行时.助动词（do,did） + 动词原形如：He is late for school.be + 形容词He is going to school.be + 动词ingWhat do you want to do?助动词do + ...还想麻烦您一下，在一个有助动词的句子中，助动词后一定要加动词吗？是的，如He doesn't like English.doesn't 为否定助动词，like为动词原型Do you speak Chinese？Do 为助动词，speak为动词原型Would you like some bread？would 为情态助动词，like 为动词原型