Pick out the incorrect statement among the following

1.  In a cyclic process the change in volume is zero but work done is not zero so (1) is incorrect statement.2.  For a gas which obey’s  PVx=constantC=Rγ−1+R1−xWe can see that x can have a range of values, which can make  C  negative. Hence it is correct.3. dU=nCvdT , for an isothermal process, change in temperature is zero, hence there will be no change in internal energy.4. Using first law of thermodynamics dQ=dU+dW , for adiabatic process  dQ=0Hence,  dU=−dW. Therefore, during expansion work done is positive, the internal energy decreases.Therefore, the correct answer is  A