Water is considered to be polluted if the dissolved oxygen $(D.O.)$ content is less than ... $ppm$ :

$A$ graph of magnetic flux $(\phi)$ versus current $(I)$ is drawn for four inductors $A, B, C, D$. Which inductor has the largest value of self-inductance?

For a first order reaction at $27^{\circ} C$,the ratio of time required for $75 \%$ completion to $25 \%$ completion of reaction is

$A$ weight $W$ can be hung in any of the following four ways by using the same string. In which case is the string more likely to break?

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:

$A$ satellite $S$ moves around a planet $P$ in an elliptical orbit as shown in the figure. The ratio of the speed of the satellite at point $a$ to that at point $b$ is