RRB Group D 1 Dec 2025 Shift 1 Solved Paper

Concept:Formic acid is the simplest carboxylic acid, with a single carbon atom, a hydroxyl group ($-\mathrm{OH}$) and a carbonyl group ($\mathrm{C}= \mathrm{O}$).Explanation:The molecular formula for formic acid is $\mathrm{HCOOH}$.It contains one carbon, two hydrogens, and two oxygen atoms.Option B ($\mathrm{HCOOH}$) matches exactly.Option A ($\mathrm{C}_2\mathrm{H}_6\mathrm{O}$) is ethanol, an alcohol.Option C ($\mathrm{C}_2\mathrm{H}_4\mathrm{O}_2$) is acetic acid, a different carboxylic acid.Option D ($\mathrm{C}_2\mathrm{H}_5\mathrm{OH}$) is also ethanol, unrelated to formic acid.Therefore, the correct formula is $\mathrm{HCOOH}$.Answer:$\mathrm{HCOOH}$