In the cylinder shown below the two pistons are connected by a string. Assume that the piston can move freely, what happens when the gas trapped between the pistons are heated?

Question

$\begin{array}{1 1} \text{both pistons will move to the left} \\ \text{both pistons will move to the right} \\ \text{both pistons will move away from each other} \\ \text{both pistons will remain stationery} \end{array}$