Which of the following is an example of an interstitial hydride?

$A$ solid cylinder of density $\rho_0$, cross-section area $A$ and length $l$ floats in a liquid of density $\rho$ $(> \rho_0)$ with its axis vertical, as shown. If it is slightly displaced downward and released, the time period of oscillation will be:

If the angles made by a straight line with the coordinate axes are $\alpha, \frac{\pi}{2}-\alpha, \beta$,then $\beta$ is equal to

If a spherical balloon has a variable diameter $3x + \frac{9}{2}$,then the rate of change of its volume with respect to $x$ is

The ascent of xylem sap in plants is mainly accomplished by the:

If $A$ and $B$ are two events such that $A \subset B$ and $P(B) \neq 0$,then which of the following is correct?