Pronoun : - Pronouns are words that take the place of nouns. We often use them to avoid repeating the nouns that they refer to. Examples are 'it', 'she', 'something', and 'myself'. '

Relative Pronoun: - are words that add information about a noun or tell the relationship between different things. A relative pronoun is a word, such as : who, whom, that or which that is used to introduce a relative clause. These words are called relative pronouns. The compounds whoever, whomever and whichever are also relative pronouns.

In other words, A pronoun which is used to begin a subordinate clause can be referred to as a relative pronoun, since it indicates the relationship of thee subordinate clause to the rest of the sentence. A subordinate clause which is introduced by a relative pronoun is often referred to as a relative clause .

Example : - The door, which is dark blue, is very tight. Here , which is a relative pronoun as it is used in a non-defining clause that refers to a person, animal or thing .

In the question : -

The park, __________ we had first met, is being renovated. Here , where is the correct relative pronoun as it is used to refers to a place .

Thus , the Correct Option is C , which is where .

Pronoun : - A pronoun is used in the place of a noun. It substitutes the noun in a paragraph or piece of writing to avoid repetition of the noun. Pronouns can be used in singular and plural forms.They usually refer back to a noun used earlier in the sentence, and they must match the number, point of view, and gender of the noun.

Relative Pronoun: - are words that add information about a noun or tell the relationship between different things. A relative pronoun is a word, such as : who, whom, that or which that is used to introduce a relative clause. These words are called relative pronouns. The compounds whoever, whomever and whichever are also relative pronouns.

In other words, A pronoun which is used to begin a subordinate clause can be referred to as a relative pronoun, since it indicates the relationship of thee subordinate clause to the rest of the sentence. A subordinate clause which is introduced by a relative pronoun is often referred to as a relative clause .

Example : - The woman, who is wearing red saree, is a doctor. Here , who is a relative pronoun as it refers to the noun woman .

In the question : -

1. The teacher appreciated the student who solved the math problem. In this sentence , who is the correct relative pronoun as it refers to the noun student

2. I love the ukulele that my aunt bought me. In this sentence , that is the correct relative pronoun as it refers in a defining clause that refers to a person, animal or thing .

3. Teena did not return the white bag that she borrowed. In this sentence , that is the correct relative pronoun as it refers in a defining clause that refers to a person, animal or thing .

Thus , the Correct Option is B  , which is who , that , that .

Pronoun : - A pronoun (I, me, he, she, herself, you, it, that, they, each, few, many, who, whoever, whose, someone, everybody, etc.) is a word that takes the place of a noun. In the sentence shiva saw shaina, and he waved at her, the pronouns he and her take the place of shiva and shaina, respectively.

Relative Pronoun :-  are words that add information about a noun or tell the relationship between different things. A relative pronoun is a word, such as : who, whom, that or which that is used to introduce a relative clause. These words are called relative pronouns. The compounds whoever, whomever and whichever are also relative pronouns.

In other words, A pronoun which is used to begin a subordinate clause can be referred to as a relative pronoun, since it indicates the relationship of thee subordinate clause to the rest of the sentence. A subordinate clause which is introduced by a relative pronoun is often referred to as a relative clause .

Example : - The woman, who is wearing red saree, is a doctor. Here , who is a relative pronoun as it is used to refer to the people in the sentence .

In the question : -

1. The car that was stolen last month was found in a river. In this sentence , that is the correct relative pronoun as it is used in a defining clause that refers to a person, animal or thing .

2. Susan is the girl whom I was talking about. In this sentence , whom is the correct relative pronoun  as it refers to the object . Here, the noun Diya receives the action in the sentence which is whom i was talking about .

Thus , the Correct Option is D , which is that , whom .