If A says, "B’s father C is the only son of my father-in-law D", then how is E, who is the sister of B, related to D?

Grand Daughter

↑ or ↓ ⇒ Upward or downward line shown "generation gap" .

   =    ⇒ Double lines shown "relation b/w Husband & Wife"

   —   ⇒ single line shown "relation in same generation other than Husband & Wife".

   +   ⇒ Plus sign shown " Male".

   -   ⇒ Plus sign shown " Female".

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ATQ,

The 4th option is satisfy the equation.

Therefore, 4th option is correct.