A U-tube contains two liquids in static equilibrium: water of density, ${\rho }_{\mathrm{w}}$$=1000 \mathrm{kg} {\mathrm{m}}^{-3}$ is in the right arm, oil of unknown density $\rho$ is in the left arm as shown in figure. Measurements give, $l=135 \mathrm{mm}$ and $d=12.5 \mathrm{mm}$. The density of oil is,

Assertion: Density of a hollow body is always less than the density of substance of equal mass of the body.

Reason: Volume of a hollow body is greater than the volume of substance of the body but mass of a hollow body is equal to the mass of substance of the body.

Assertion: A hydrogen filled balloon stop rising after it has attained a certain height in the sky.

Reason: The atmospheric pressure decreases with height and becomes zero when maximum height is attained.

Assertion: The size of a hydrogen balloon increases as it rise in air.

Reason: The material of the balloon can be easily stretched.

Assertion: The shape of an automobile is so designed that its front resembles the streamline pattern of the fluid through which it moves.

Reason: The shape of the automobile is made streamlined in order to reduce resistance offered by the fluid.

Assertion: For Reynold number $\mathrm{Re}>2000$, the flow of fluid is turbulent.

Reason: Inertial forces are dominant compared to the viscous forces at such high Reynold numbers.