b
(b)
Let the difference between $2 \operatorname{limbs}$ be $x$
Pressure on the line $Y Y$ should be same below both limbs, so
$\rho_{\text {glycerine }} \times g \times h=\rho_{\text {water }} \times g \times(h+x)$
$\Rightarrow 1.2 \times 10=1 \times(h+x)$
$\Rightarrow 2 \,cm =x$
