A vessel of area of cross-section A has liquid to a height H. There is a hole at the bottom of vessel having area of cross-section a. The time taken to decrease the level from \[{{H}_{1}}\] to \[{{H}_{2}}\] will be

• A.             \[\frac{A}{a}\sqrt{\frac{2}{g}}[\sqrt{{{H}_{1}}}-\sqrt{{{H}_{2}}}]\]                                
• B.             \[\sqrt{2gh}\]
• C.             \[\sqrt{2gh\,({{H}_{1}}-{{H}_{2}})}\]                                       
• D.              \[\frac{A}{a}\sqrt{\frac{g}{2}}[\sqrt{{{H}_{1}}}-\sqrt{{{H}_{2}}}]\]