A constant amount of gas is contained in a cylinder fitted with a movable piston. At first, the gas has pressure $p_1$ and volume $V_1$. The temperature is maintained unchanged. The piston is then shifted so that the pressure changes to $p_2$ and the volume changes to $V_2$. Which equation is correct?
- A$\frac{p_1}{V_1} = \frac{p_2}{V_2}$
- B$\frac{p_1}{p_2} = \frac{V_1}{V_2}$
- C$p_1 V_1 = p_2 V_2$
- D$p_1 V_2 = p_2 V_1$