A, B, C, and D are four people who attended a seminar on different days: Monday, Tuesday, Wednesday, and Thursday. A attended before C but after B. D attended on Wednesday. What day did C attend the seminar?
In a family, there are four members: P, Q, R, and S. P is the father of Q, Q is the mother of R, and S is the sister of R. What is the relationship between P and S?