When this or that is used in the first part of the sentence, the tag question should be used it.
Example: This is your book, isn't it?
When these or those is used in the first part of the sentence, the tag question should be used they
Example: These are your shoes, aren't they?
When the subject everybody, anybody somebody, someone, etc. so the tag question should be used they
Example: Nobody stayed there, did they?
Someone is staring at her, aren't they?
