Which of the following reagents / reactions will convert 'A' to 'B'?

The conversion requires transformation of a terminal alkene into an aldehyde.

Hydroboration-oxidation using $$\mathrm{BH_3}$$ followed by $$\mathrm{H_2O_2/OH^-}$$ converts the alkene into a primary alcohol through anti-Markovnikov addition.

$$\mathrm{R-CH=CH_2 \xrightarrow[BH_3]{H_2O_2/OH^-} R-CH_2-CH_2OH}$$

The primary alcohol is then oxidised using $$\mathrm{PCC}$$ which selectively converts primary alcohols into aldehydes without further oxidation to carboxylic acids.

$$\mathrm{R-CH_2OH \xrightarrow{PCC} R-CHO}$$

Therefore, the required reagents are:

$$\mathrm{BH_3,\ H_2O_2/OH^- \ followed\ by\ PCC}$$

Thus, the right option is going to be $$\mathrm{C}$$