Two narrow tubes of diameters $d_1$ and $d_2$ are joined together to form a $U$-tube open at both ends. If the $U$-tube contains water,the difference in water levels in the limbs is ($T$ is the surface tension of water,the angle of contact is zero,the density of water is $\rho$,and $g$ is the acceleration due to gravity).

• A
  $\frac{4 T}{\rho g}\left[\frac{d_2-d_1}{d_1 d_2}\right]$
• B
  $\frac{4 T}{\rho g}\left[\frac{d_1 d_2}{d_1+d_2}\right]$
• C
  $\frac{2 T}{\rho g}\left[\frac{d_2-d_1}{d_1 d_2}\right]$
• D
  $\frac{2 T}{\rho g}\left[\frac{d_1+d_2}{d_1 d_2}\right]$