What would be the most likely value for CT , the molar heat capacity at constant temperature

(A) 0

(B) 0

(C) CV

(D) CT = ∞

The correct option is (A).
Molar heat capacity at constant temperature (C_T) is defined as the amount of heat required to raise the temperature of 1 g of gas through 1̊ C keeping its temperature constant. But it is impossible to rise the temperature of 1 g of gas through 1̊ C keeping its temperature constant. So the two statements contradict to each other. Thus the most likely value for molar heat capacity at constant temperature (C_T) will be zero. Therefore option (A) is correct.