Consider the following properties :

$\begin{array}{cc}\ &\text{P. temperature} & \text{Q. specific gravity} \\ &\text{R. chemical potential} & \text{ S. volume} \\ \\ \end{array}$

The option which lists $ALL$ the intensive properties is

1. $P$
2. $P$ and $Q$
3. $P$, $Q$ and $R$
4. $P$, $Q$, $R$ and $S$