In a family, there are three siblings: X, Y, and Z. X is a lawyer, Y is a doctor, and Z is the youngest. If Z is not the lawyer, who is the oldest sibling?
In a group of items: P, Q, R, and S, the following rules apply: 1) P cannot be chosen if Q is chosen. 2) R must be chosen if S is not chosen. Which of the following selections is valid?