The phenomenon of 'industrial melanism' demonstrates:

Nerve cells do not divide because they do not have:

What are $\underline{A}, \underline{B}, \underline{C}$ in the following reactions?
$(I)$ $(CH_3 CO_2)_2 Ca \xrightarrow{\Delta} \underline{A}$
$(II)$ $CH_3 CO_2 H \xrightarrow[Red\ P]{HI} \underline{B}$
$(III)$ $2 CH_3 CO_2 H \xrightarrow{P_4 O_{10}} \underline{C}$
$\underline{A} \quad \underline{B} \quad \underline{C}$

The coil in a moving coil galvanometer experiences a torque proportional to the current passing through it. If a steady current $i$ is passed through it,the steady deflection of the coil is found to be $90^o$. Now,the steady current is switched off and a charge $q$ is suddenly passed through the coil. If the coil has $N$ turns of area $A$ and its moment of inertia is $I$ about the axis of rotation,then the maximum angle through which it deflects upon passing charge $q$ is:

The centre of mass of a body

Assertion $(A)$: $K, Rb$ and $Cs$ form superoxides.
Reason $(R)$: The stability of the superoxides increases from $K$ to $Cs$ due to decrease in lattice energy.
The correct answer is