What is the protein coat of a virus known as?

The potential energy function for the force between two atoms in a diatomic molecule is approximately given by $U(x) = \frac{a}{x^{12}} - \frac{b}{x^6}$,where $a$ and $b$ are constants and $x$ is the distance between the atoms. If the dissociation energy of the molecule is $D = [U(x = \infty) - U_{\text{equilibrium}}]$,what is the value of $D$?

$A$ block of mass $2 \ kg$ slides down an inclined plane of inclination $30^{\circ}$. The coefficient of friction between the block and the plane is $0.5$. The contact force between the block and the plane is:

Haploid plants are obtained from which of the following?

If $\triangle ABC$ is right-angled at $A$,then $r_2+r_3$ is equal to

Which option is correct to match section $A$ with section $B$?

Section $A$	Section $B$
$(i)$ Nitrosomonas	$(a)$ $\text{Nitrite} \rightarrow \text{Nitrate}$
$(ii)$ Agrobacterium	$(b)$ $\text{Nitrogen fixing bacteria}$
$(iii)$ Rhizobium	$(c)$ $\text{NO}_3^- \rightarrow \text{N}_2$
$(iv)$ Nitrobacter	$(d)$ $\text{Ammonia} \rightarrow \text{Nitrite}$
	$(e)$ $\text{Denitrifying bacteria}$