An ideal gas is contained in a vessel. It is heated at constant pressure. Fraction of the heat energy supplied that converts to work done by the gas is:

• A

  $\mathrm{\gamma }$

• B

  $\frac{1}{\mathrm{\gamma }}$

• C

  $\text{1-}\frac{1}{\mathrm{\gamma }}$

• D

  $\mathrm{\gamma }-1$