A planet of mass m moves around the sun of mass M in an elliptical orbit. The maximum and minimum distances of the planet from the sun are \[{{r}_{1}}\] and \[{{r}_{2}}\]. respectively. The time period of the planet is proportional to

• A.  \[{{r}_{1}}^{\frac{3}{2}}\]                           
• B.         \[{{r}_{2}}^{\frac{3}{2}}\]
• C.  \[\frac{{{({{r}_{1}}+{{r}_{2}})}^{\frac{3}{2}}}}{2}\]             
• D.         \[\frac{{{({{r}_{1}}-{{r}_{2}})}^{\frac{3}{2}}}}{2}\]