(d)
For the conversion of primary alcohol into aldehyde with the same number of carbon, the most suitable reagent is pyridinium chlorochromate (PCC).
$\ \ \ \ \ \ \ \ \ \ RCH_{2}OH\ \overset{\ \ \ PCC\ \ \ \ }{\rightarrow}RCHO$
Note PCC is the mixture of pyridine, $CrO_{3}$ and $HCl\$ in 1:1:1 ratio.