In a family of six persons A, B, C, D, E and F, the professions are lawyer, doctor, teacher, salesman, engineer and accountant. D, who is the salesman, is married to the lady who is the teacher. The doctor is married to the lawyer. F, the accountant, is the son of B and brother of E. C, the lawyer, is the daughter-in-law of A. E is the unmarried engineer and A is the grandmother of F. How is D related to F?

Introduction / Context:
This is a more complex family and profession puzzle. It requires you to track who is married to whom, who is whose child, and who has which profession. After building the entire family structure, you must answer a specific question about the relationship between D and F.

Given Data / Assumptions:

• The six members are A, B, C, D, E and F.
• The professions are lawyer, doctor, teacher, salesman, engineer and accountant.
• D is the salesman and is married to the lady teacher.
• The doctor is married to the lawyer.
• F is the accountant, the son of B and the brother of E.
• C is the lawyer and the daughter-in-law of A.
• E is the unmarried engineer.
• A is the grandmother of F.
• There are exactly two married couples in the family.

Concept / Approach:
The plan is to identify the married couples and then place everyone into generations. From the daughter-in-law clue, we can identify one couple, and from the salesman and teacher clue, the other couple. Once that structure is clear, the generational positions of D and F can be compared to determine whether D is a father, grandfather, uncle or brother of F.

Step-by-Step Solution:
Step 1: From "C is the lawyer and the doctor is married to the lawyer", it follows that C is the lawyer spouse and the doctor is married to C.Step 2: C is also the daughter-in-law of A, which means C is married to A son. Therefore, the doctor, who is C spouse, is A son.Step 3: F is the accountant, son of B and brother of E. We also know that A is the grandmother of F. Thus A is the mother of B, and B is a child of A.Step 4: Since the doctor must be the son of A and is also a distinct member from A and C, B fits this role. So B is the doctor and is married to C, the lawyer. This forms one married couple: B and C.Step 5: The second married couple uses D, the salesman, who is married to the lady teacher. The only remaining female who can be the teacher is A, because C is the lawyer and E is the engineer. Thus A is the teacher and is married to D, the salesman.Step 6: A is stated to be the grandmother of F. If A is married to D, then D is A husband and stands in the same grandparent generation as A.Step 7: Therefore, D is the grandfather of F.

Verification / Alternative check:
Summarise the arrangement. Couple one: D (salesman, grandfather) married to A (teacher, grandmother). Couple two: B (doctor, son of A and D) married to C (lawyer, daughter-in-law of A and D). Their children are F (accountant, son of B and C) and E (unmarried engineer). This assignment satisfies every condition given. From this family tree, D is clearly one generation above F as the husband of F grandmother, making him F grandfather.

Why Other Options Are Wrong:
D is not the father of F, because B is explicitly given as the parent of F. D is not F uncle, because uncles are siblings of parents, but D is the parent of B, not B sibling. D is not F brother, since he is one generation older. There is no information supporting D as a cousin of F. The only correct generational relationship is that D is F grandfather.

Common Pitfalls:
A common source of confusion is mixing up the two married couples or misassigning professions, such as trying to make A the lawyer or C the teacher. Another error is forgetting that A is the grandmother of F, which forces A into the older generation and ensures that the teacher married to D is in the grandparent generation. Always verify that every clue is used; if any statement is left unused, your arrangement may be incomplete or inconsistent.

Final Answer:
D is related to F as his grandfather.