When one mole of monoatomic ideal gas at T K undergoes adiabatic change under a constant external pressure of 1 atm changes volume from 1 litre to 2 litre. The final temperature in Kelvin would be
A. `(T)/(2^((2//3)))`
B. `T+(2)/(3xx0.0821)`
C. T
D. `T-(2)/(3xx0.0821)`
