A is the sister of B, who is the mother of C. C is the mother of D. E is the grandmother of D. How is C related to E?

Introduction / Context:
This puzzle links two generations of one family with an additional person E, who is stated to be the grandmother of D. You know that C is D's mother, and B is C's mother, so B is also a grandmother of D. The task is to place E in relation to these people so that all clues fit and then determine how C is related to E. This type of question tests your ability to recognise that a child can have two grandmothers (maternal and paternal).

Given Data / Assumptions:
- A is the sister of B. - B is the mother of C. - C is the mother of D. - E is the grandmother of D. - A, B, C and D are already inside one line of descent. - We assume E is a different person from B, since a separate letter is used.

Concept / Approach:
From the chain B → C → D, B is clearly one grandmother of D (the maternal grandmother). The question also mentions that E is the grandmother of D, so E must be the other grandmother, that is, the paternal grandmother (the mother of D's father). In that case, C is the wife of E's son and therefore E's daughter-in-law. The key concept is that D has two grandmothers: one from the mother's side and one from the father's side.

Step-by-Step Solution:
Step 1: B is the mother of C and C is the mother of D, so B is the maternal grandmother of D. Step 2: E is also described as the grandmother of D. Since B already occupies the role of maternal grandmother, and E is clearly a distinct person (different name), E must be D's paternal grandmother. Step 3: A paternal grandmother is the mother of D's father. Let D's father be F. Then E is the mother of F. Step 4: C is the mother of D and therefore the wife of F (D's father) in a typical family structure. Step 5: If E is the mother of F and C is the wife of F, then C is related to E as her daughter-in-law. Step 6: Thus, C is the daughter-in-law of E.

Verification / Alternative check:
Construct a family tree: generation 1 – E and B (in different lineages); generation 2 – F as E's son, B's children A and C; generation 3 – C and F are married and have D. From D's perspective, B is the mother of C and thus maternal grandmother; E is the mother of F and thus paternal grandmother. From E's perspective, C is her son's wife, that is, daughter-in-law. This diagram satisfies every statement in the question.

Why Other Options Are Wrong:
- Sister: C and E are clearly from different generations; they cannot be sisters. - Daughter: If C were E's daughter, then E would be the grandmother of D via the maternal line, contradicting B's role as maternal grandmother. - Mother: C is the mother of D, not the mother of E. - Aunt: An aunt is a sibling of a parent. E is not positioned as C's sibling, and the relation being asked is C to E, not C to D.

Common Pitfalls:
A frequent error is to overlook that a child can have two grandmothers and to assume E must be the same as B. However, the use of a separate letter strongly implies a different person. Another pitfall is not distinguishing between maternal grandmother (mother's mother) and paternal grandmother (father's mother). Keeping track of which side of the family each person belongs to is essential in solving such questions.

Final Answer:
C is related to E as her daughter-in-law.