"must"后面必须加 动词原形。例如：
1. She must be the teacher, she always looks so serious.
2. They must not be at home right now.
3. You must finish your homework before you go out.
"must"是情态动词，后面必须接动词原形，表示对某事或某人的强烈肯定或命令。
"must"后面必须加 动词原形。例如：
1. She must be the teacher, she always looks so serious.
2. They must not be at home right now.
3. You must finish your homework before you go out.
"must"是情态动词，后面必须接动词原形，表示对某事或某人的强烈肯定或命令。