'P @ Q' means 'P is the mother of Q'
'P & Q' means 'P is the wife of Q'
'P # Q' means 'P is the husband of Q'

If 'A # B @ C @ D & E', then how is D related to A?

Let's decode the given expression 'A # B @ C @ D & E' step-by-step from left to right:
A # B → A is the husband of B. (B is a female, A is a male)

B @ C → B is the mother of C. (So, A and B are parents of C)

C @ D → C is the mother of D. (C is a female, making her the daughter of A and B)

D & E → D is the wife of E. (D is a female)

From this tree:

A and B are a married couple.

Their daughter is C.

C's daughter is D.

Therefore, D is the daughter of A's daughter, which means D is the Daughter's daughter of A.