（1）当名词是单数可数名词或不可数名词时， 用is. 当名词是复数的可数名词时，用are.
There‘s a man at the door. 门口有个人 。
There be 是英语中常用句型， 表示“有”。
eg: There is some apple juice in the bottle. There are some strangers in the street.
