Which of the following has the highest heat of hydrogenation?

Product $A$ of the above reaction is

Match the following reactions in List-$I$ with their products in List-$II$:
| List-$I$ | List-$II$ |
| :--- | :--- |
| $A. HC \equiv CH \xrightarrow{Hg^{2+}, H^{+}/H_{2}O}$ | $I. H_{3}C-COOH$ |
| $B. CH_{4} \xrightarrow{O_{2}, Mo_{2}O_{3}, \Delta}$ | $II. CH_{3}-CO-CH_{3}$ |
| $C. (CH_{3})_{2}C=C(CH_{3})_{2} \xrightarrow{O_{3}, Zn, H_{2}O}$ | $III. H_{3}C-CHO$ |
| $D. CH_{3}-CH=CH-CH_{3} \xrightarrow{KMnO_{4}, H^{+}}$ | $IV. HCHO$ |

The maximum number of structural isomers possible for the hydrocarbon having the molecular formula $C_4H_6$ is:

What is the difference in terms of molar masses of the second and fourth members of a homologous series?

The state of hybridisation of $C_2, C_3, C_5$ and $C_6$ of the hydrocarbon $CH_3-C_6(CH_3)_2-C_5H=C_4H-C_3H(CH_3)-C_2 \equiv C_1H$ is in the following sequence: