The isothermal bulk modulus of a perfect gas at normal pressure is 

• A

  $1.013\times {10}^{6}N/m^2$

• B

  $1.013\times {10}^{-11}N/m^2$

• C

  $1.013\times {10}^{+5}N/m^2$

• D

  $1.013\times {10}^{+11}N/m^2$