Vivek said, "This boy is the husband of the only granddaughter of my father." How is Vivek related to the boy?

Let's break down the relationship described in the statement.

Vivek says: "This boy is the husband of the only granddaughter of my father."

Starting from Vivek's perspective:

"My father" refers to Vivek's father.

"The only granddaughter of my father" refers to the granddaughter of Vivek's father.

A granddaughter of Vivek's father would be the daughter of Vivek's father's child. Since Vivek is a child of his father, the granddaughter would be Vivek's daughter.

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Now we can establish the relationship:

The only granddaughter of Vivek's father = Vivek's daughter

"This boy" = The husband of Vivek's daughter

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The husband of one's daughter is called a son-in-law.

From the boy's perspective, Vivek would be his father-in-law.

Therefore, Vivek is related to the boy as his Father-in-law.

The answer is Option 3: 3