Which one of the following ecosystem types has the highest annual net primary productivity?

The resolving power of an astronomical telescope is $0.2\, sec$. If the central half portion of the objective lens is covered,the resolving power will be....$sec$

$A$ stone tied to a string of length $L$ is whirled in a vertical circle,with the other end of the string at the center. At a certain instant of time,the stone is at its lowest position and has a speed $u$. The magnitude of the change in its velocity as it reaches a position where the string is horizontal is

The intensity of the electric field required to keep a water drop of radius $10^{-5} \, cm$ just suspended in air when charged with one electron is approximately:

State the electronic configurations of group-$16$ elements.

Consider the following reaction:
$C_6H_5COCl \xrightarrow{H_2, Pd-BaSO_4} 'A'$
The product $'A'$ is: