What is the meaning of a "responsible third party" in Texas law?

Group of answer choices

Any party who may be responsible for causing the plaintiff's injuries.

A party who may be responsible for causing the plaintiff's injuries and is a named defendant to the plaintiff$$s lawsuit.

A party who may be responsible for the plaintiff's injuries, but who is not a named defendant to the plaintiff$$s lawsuit.

A party who has no connection to the incident that caused the plaintiff's injuries, but who may still be sued by the plaintiff for damages.