The answer is"A". Because the pronoun used in the question is demonstrative pronoun.

Demonstrative Pronoun

A demonstrative pronoun is used to point to a specific person, place, or thing. It can be used to indicate something nearby or far away. In the given sentence, the word "that" is used to point out a specific stain. Hence, the correct answer is option 'A', which is demonstrative pronoun.

Example: This is my book. That is your book.

In the above example, "this" and "that" are used to point to specific books. "This" refers to the book belonging to the speaker, while "that" refers to the book belonging to the listener.

Personal Pronoun

A personal pronoun is used to refer to a specific person or group of people. It can be used as a subject or object in a sentence. Examples of personal pronouns include I, me, you, he, she, it, we, and they.

Example: She gave me the book.

In the above example, "she" is a personal pronoun used to refer to a specific person. "Me" is also a personal pronoun used as an object.

Indefinite Pronoun

An indefinite pronoun is used to refer to a non-specific person, place, or thing. Examples of indefinite pronouns include anyone, anything, someone, and something.

Example: Someone left their coat in the classroom.

In the above example, "someone" is an indefinite pronoun used to refer to a non-specific person.

Relative Pronoun

A relative pronoun is used to connect a clause or phrase to a noun or pronoun. Examples of relative pronouns include who, whom, whose, which, and that.

Example: The book that I read was very interesting.

In the above example, "that" is a relative pronoun used to connect the clause "I read" to the noun "book".