Wires $P$ and $Q$ have the same resistance at room temperature. When heated,the resistance of $P$ increases and that of $Q$ decreases. We conclude that:

• A
  $P$ and $Q$ are conductors of different materials
• B
  $P$ is $N$-type semiconductor and $Q$ is $P$-type semiconductor
• C
  $P$ is a conductor and $Q$ is a semiconductor
• D
  $P$ is a semiconductor and $Q$ is a conductor