主要是看There be 结构后面接的名词~
若后面接的名词是可数名词复数那就用复数~
比如 There are many students.
若后面的名词是可数名词单数则用单数~
比如 There is a girl in the classroom.
若后面接的名词是不可数名词则用单数
比如 There is some meat in the fridge.