The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 $\mathrm{\Omega }$ is : 

• A

  1.0 $\mathrm{\Omega }$

• B

  0.2 $\mathrm{\Omega }$

• C

  0.5 $\mathrm{\Omega }$

• D

  0.8 $\mathrm{\Omega }$