The number of significant figures in $23.023$,$0.0003$,and $2.1 \times 10^{-3}$ are respectively:

Which selection method is used for vegetative propagation in plants?

If $y = a \sin x + b \cos x$,then $y^2 + \left( \frac{dy}{dx} \right)^2$ is a

$A$ river is flowing from east to west at a speed of $5\ m/min$. $A$ man on the south bank of the river,capable of swimming $10\ m/min$ in still water,wants to swim across the river in the shortest time. He should swim:

Which of the following statements are true about acceleration due to gravity $(g)$ of the earth (where $r$ is distance from the centre of the earth and $R$ is the radius of the earth)?
$(a)$ $g$ decreases in moving away from the centre,if $r > R$.
$(b)$ $g$ decreases in moving away from the centre,if $r < R$.
$(c)$ $g$ is zero at the centre of the earth.
$(d)$ $g$ at the equator decreases,if the earth stops rotating about its axis.

Which of the following hydrides has the lowest boiling point?