1. I and II are ______. (A) constitutional isomers. (B) enantiomers. (C) identical. (D) diastereomers. (E) not isomeric.

4. An optically active compound, A, with the molecular formula $\mathrm{C_7H_{12}}$ reacts with cold dilute $\mathrm{KMnO_4}$ and gives IR absorption at about $3300~\mathrm{cm^{-1}}$. On catalytic hydrogenation, A is converted to B ($\mathrm{C_7H_{16}}$), and B is also optically active. Which is a possible structure for A? (A) I (B) II (C) III (D) IV (E) V (F) V