The correct option is
C P1T2V2=P2T1V1Charles' law is the change in volume with respect to temperature at constant pressure, while Boyle's law is the change in volume with respect to pressure at a constant temperature.
Taking a gas of volume V1, pressure P1 and temperature T1, and let its change have a state (V2,P2,T2), then according to Boyle's law,
P1V1=P2V2 ..........(1)
Then keeping this constant pressure, move to state (V2,P2,T2) using Charles' law,
V2T1=V2T2 .........(2)
Solving for V2, in both (1) and (2) and then equating them, we get-
P1V1T1=P2V2T2
After changing the pressure, volume and temperature of the gas, still their product is equal, suggesting that the relation is constant: PVT=k.
Hence, the correct answer is option B.