Consider the following statements about homologous series of carbon compounds :

(a) All succeeding members differ by $-\mathrm{CH}_2$ unit.

(b) Melting point and boiling point increases with increasing molecular mass.

(c) The difference in molecular masses between two successive members is $16\text{ u}$.

(d) $\mathrm{C}_2\mathrm{H}_2$ and $\mathrm{C}_3\mathrm{H}_4$ are NOT the successive members of alkyne series.

The correct statements are -

Let us analyze each statement based on the properties of a homologous series:

• Statement (a) is correct: Successive members of a homologous series differ by a $-\mathrm{CH}_2$ unit.
• Statement (b) is correct: As the molecular mass increases in any homologous series, the physical properties show a gradation. The melting and boiling points increase with increasing molecular mass due to stronger intermolecular forces of attraction.
• Statement (c) is incorrect: The difference in molecular mass between two successive members (differing by a $-\mathrm{CH}_2$ unit) is $14\text{ u}$ (since Carbon $= 12\text{ u}$ and Hydrogen $= 1\text{ u} \times 2 = 2\text{ u}$), not $16\text{ u}$.
• Statement (d) is incorrect: $\mathrm{C}_2\mathrm{H}_2$ (ethyne) and $\mathrm{C}_3\mathrm{H}_4$ (propyne) differ by exactly one $-\mathrm{CH}_2$ unit and belong to the same general formula $\mathrm{C}_n\mathrm{H}_{2n-2}$ (alkynes). Thus, they are successive members of the alkyne series.

Therefore, only statements (a) and (b) are correct, which corresponds to option A.