A tube of length /r, which is wide enough to male surface tension effects negligible, is closed at one end. It is then lowered into a tank of mercury to a depth.h as shown in fig. (4), so that mercury rises a distance x into 

the tube. If the mercury barometer stands at i also, then
 

• A

  ${\text{(2h−x)(h−x)=h}}^2$

• B

  $\mathrm{h}(\mathrm{h}-\mathrm{x})={\mathrm{h}}^2$

• C

  $(2\mathrm{h}-\mathrm{x})(\mathrm{h}+\mathrm{x})={\mathrm{h}}^2$

• D

  $2\mathrm{h}(\mathrm{h}-\mathrm{x})={\mathrm{h}}^2$