d
According to principle of continuity, for streamline flow of fluid
through a tube of non-uniform cross-section the rate of flow of fluid
(Q) is same at every point in the tube.
$Av =$ constant $\Rightarrow A _{1} v _{1}= A _{2} v _{2}$
Therefore, the rate of flow of fluid is same at $M$ and $N$.