Oxidation of alcohols depends both on the class of alcohol and on the strength of the oxidising agent. Primary alcohols can in principle be oxidised first to aldehydes and then further to carboxylic acids, but the second step requires water and a strong oxidant. Pyridinium chlorochromate, PCC, is a mild oxidant used in anhydrous medium that stops cleanly at the aldehyde stage, so the principal product from a primary alcohol is an aldehyde, the correct answer. A carboxylic acid is wrong because PCC does not over-oxidise; that outcome needs reagents like acidified potassium dichromate or permanganate in aqueous conditions. A ketone is impossible from a primary alcohol because a ketone requires a secondary alcohol with the carbonyl on an internal carbon. An ester cannot form from a single alcohol under simple oxidation. This selective control is part of NCERT alcohol chemistry and a common JEE reagent-selection question. As a plausibility check, the defining feature of PCC is halting oxidation at the aldehyde, which matches the stated product.