Fill in the blank with a suitable interrogative pronoun:
________ did you consult regarding your falling health?
A. What
B. Whom
C. Whose
D. Which

Hint:Word that is used in place of a noun is known as pronouns. Pronouns are the subpart of nouns. To avoid any repetition of the noun, pronouns are used. Pronouns are of different forms for the different ways we use them. Pronouns are he, she, they, it, whom, and so forth.

Complete answer:
Pronouns (such as each, few, he, she, I, herself, who, whoever, whose, that, they, etc) are used to avoid the repetition of nouns. for example in a sentence- Rakhi and Leena went to the market. Rakhi and Leena bought some apples. Rakhi and Leena returned home after 8 pm.

In the above sentences nouns 'Rakhi and Leena' are repeated. Hence to avoid this repetition we will use pronouns. On replacing the nouns with pronouns we will write it as:
Rakhi and Leena went to the market. They bought some apples. They home after 8 pm.
In the above sentence, the Proper noun 'Rakhi and Leena' is replaced by the pronoun 'they'.
An interrogative pronoun is a type of pronoun which is used to ask questions. The correct option was the given sentence will be option B. Whom.
Whom did you consult regarding your falling health?

In the given sentence the interrogative pronoun is 'whom' which is used to ask questions about people. Whose as a interrogative pronoun is related to possession.

Let’s know why other options are incorrect:
Option A. What as an interrogative pronoun is used to ask questions about a situation.
Option C. Whose as an interrogative pronoun is related to possession and to ask about people and objects.
Option D. Which is used to ask questions about objects.

Hence the correct answer is option ‘B’

Note:While using the interrogative pronouns one must be careful about the subject and the object before using the interrogative pronoun. The object is what or who the action is being done to and the subject is what or who is doing an action, or a situation described by the verb.