Human urine is usually acidic because:

$A$ rectangular glass slab $ABCD,$ of refractive index $n_1,$ is immersed in water of refractive index $n_2$ $(n_1 > n_2)$. $A$ ray of light is incident at the surface $AB$ of the slab as shown. The maximum value of the angle of incidence $\alpha_{\max},$ such that the ray comes out only from the other surface $CD,$ is given by:

Which one of the following molecular hydrides acts as a Lewis acid?

$A$ point moves in the $xy$-plane such that the sum of its distances from two mutually perpendicular lines is always equal to $5$ units. The area (in sq units) enclosed by the locus of the point is

Boron in green plants assists in

Let a random variable $X$ have a Binomial distribution with mean $8$ and variance $4$. If $P(X \leq 2) = \frac{k}{2^{16}}$,then $k$ is equal to: