In a family of five members A, B, C, D, and E, A is a doctor, B is a teacher, C is the mother of D, D is a student, and E is the father of A. Who is the teacher?
A can complete a work in 12 days, and B can complete the same work in 18 days. If they work together, how many days will they take to complete the work?
In a family, there are three children: X, Y, and Z. X is the brother of Y, and Y is the sister of Z. If Z is a boy, who is the only girl in the family?