$A + B$ means $A$ is the son of $B$; $A - B$ means $A$ is the wife of $B$; $A \times B$ means $A$ is the brother of $B$; $A \div B$ means $A$ is the mother of $B$; and $A = B$ means $A$ is the sister of $B$. What does $P + R - Q$ mean?

• A
  $Q$ is the father of $P$.
• B
  $Q$ is the son of $P$.
• C
  $Q$ is the uncle of $P$.
• D
  $Q$ is the doctor of $P$.