为什么要加are?I am younger than you are?请问这个are有什么用?已经有be动词了啊~

I am younger than you are 为什么加个are? I am younger than you are 为什么加个are? i am very older than you are .为什么这里还要加are?不加可以吗 i am in China为什么要加am I am from the USA为什么要加am 为什么i am wanna be with you要加am I am busy yesterday为什么加am 为什么要加are?I am younger than you are?请问这个are有什么用?已经有be动词了啊~ i am so sorry / i am so cold 为什么要加so I am hardly ever late for school.为什么I后面要加am? I am not Chinese boy I am not a Chinese 为什么后者要加a那 I am going to the park .为什么要加the? Im with my sister.为什么要加am I'm leaving为什么要加am呢 i'm used to it为什么要加am I am worker 为什么要在worker前加a? i am not in this school.为什么要加in. i am always thinking.为什么要am.为什么要加ing.