To solve this problem, we need to identify the reagents that convert an alkene to an aldehyde.$\\$The transformation involves converting cyclohexyl ethene to cyclohexyl propanal.$\\$Step 1: Hydroboration-Oxidation$\\$• The first step is hydroboration using $$BH$_3. \\$• This adds across the double bond in an anti-Markovnikov manner, forming an alcohol.$\\$• The second step is oxidation using $$H$_2$O$_2/$OH$^-,$ which converts the borane intermediate to an alcohol.$\\$Step 2: Oxidation to Aldehyde$\\$• The alcohol is then oxidized to an aldehyde using PCC (Pyridinium chlorochromate).$\\$Therefore, the correct sequence of reagents is:$\\$(i) $$BH$_3,$ (ii) $$H$_2$O$_2/$OH$^-,$ (iii) PCC.$\\$This corresponds to Option 4.