Read the following statements carefully and choose the correct answer 
(i) Expansion of a gas in vacuum  $\left({\mathrm{p}}_{\mathrm{ex}}=0\right)$is called free expansion. 
(ii) Work is done during free expansion of an ideal gas whether the process is reversible or irreversible  
(iii) No work is done during free expansion of an ideal gas  whether the process is reversible or irreversible 
(iv) No work is done during free expansion of an ideal gas  when the process is reversible