After prolonged treatment of $(A)$ by $D_2O/DO^-$, the difference in molecular weights of compounds $(A)$ and $(B)$ is:

Consider the sets $I$,$II$,and $III$. Identify the set$(s)$ which is (are) correctly matched.
$I$. $\text{Staggered ethane} > \text{eclipsed ethane} \dots \dots \dots \text{torsional strain}$.
$II$. $2, 2-\text{Dimethylbutane} > 2-\text{methylpentane} \dots \dots \dots \text{boiling point}$.
$III$. $cis-\text{but}-2-\text{ene} > trans-\text{but}-2-\text{ene} \dots \dots \dots \text{dipole moment}$.

Rank the following substances in order of decreasing heat of combustion (maximum $\to$ minimum).

Which of the following statements is $NOT$ correct?

The number of chiral centres present in $[B]$ is

When isomers have the same structural formula but differ in the relative arrangement of atoms or groups,they are called ........