A is the father of B, but B is not the son of A. What is B to A?

Introduction / Context:
This is a very common and straightforward blood relation puzzle that tests whether you remember that a child can be either a son or a daughter. Many candidates automatically assume male children in these reasoning questions and miss the simple gender twist, so exam setters like to include this pattern.

Given Data / Assumptions:

• A is the father of B. So B is a direct child of A.
• B is not the son of A. So B is not male.
• We assume a simple nuclear family with no hidden adoption or step relations.
• All options are simple relations like daughter, granddaughter and so on.

Concept / Approach:
In human families, a child can be a son or a daughter. If someone is clearly the father of B but B is not a son, then B must be a daughter, because there is no other basic parent child relation that fits. The question is essentially a test of not jumping to conclusions and of reading all the information carefully.

Step-by-Step Solution:
Step 1: From "A is the father of B", we know two facts: A is male and B is a child of A.Step 2: The second statement says "B is not the son of A". This eliminates the possibility that B is a male child.Step 3: The only remaining standard possibility for a direct child is that B is a female child of A.Step 4: A female child of a person is called a daughter.Step 5: Therefore, B is the daughter of A.

Verification / Alternative check:
Try small examples. Suppose A is a man named Rohan. The statement tells you that Rohan is the father of B, so B is Rohan child. Then you are told that B is not Rohan son. The only way for someone to be a child of Rohan and not be a son is to be a daughter. Options like granddaughter or niece require extra generations or siblings that are not present in the information given.

Why Other Options Are Wrong:
A cannot be the grandfather of B because that would require one more generation, namely a parent between A and B. Son-in-law would require B to be married to A child, which is impossible if A is already B father. Granddaughter implies that B is a child of A son or daughter, not a direct child. Niece would mean B is the child of A sibling, again contradicting the direct father child statement.

Common Pitfalls:
The usual mistake is overthinking and searching for some exotic relation when the answer is simply daughter. Another mistake is to ignore the second sentence and treat B as the son of A by habit. Always read all statements before deciding; if a question mentions that someone is not a son, it is almost always guiding you to consider the daughter case.

Final Answer:
B is A daughter.