The number of isomeric tetraenes ($NOT$ containing $sp$-hybridized carbon atoms) that can be formed from the following reaction sequence is.....

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

To carry out the given conversions,select the correct option.

How many cyclic structures are possible for $C_4H_6$?

Compound $(C)$ in the above sequence of reaction is:

The product $(x)$ is