Gas in a cylinder moves a piston with area 0.20$m^2$as heat is slowly added to the system. If 2000 J of work is done on the environment by the gas and the pressure of the gas in the cylinder remains constant at$1x{10}^5$Pa, the displacement of the piston must be

• A

   10 cm            

• B

  5 cm

• C

  1 cm

• D

  100 cm