The empirical formula gives the simplest whole-number ratio of atoms in a compound and is found from percentage composition by converting each mass percentage into moles and then dividing by the smallest mole value. For carbon: 40.0 / 12 = 3.33 mol. For hydrogen: 6.7 / 1 = 6.7 mol. For oxygen: 53.3 / 16 = 3.33 mol. Dividing each by the smallest value (3.33) gives C : H : O = 1 : 2.01 : 1, which rounds to 1 : 2 : 1, so the empirical formula is CH2O. The option C2H4O2 is a multiple of the empirical formula and represents a molecular formula, not the simplest ratio, so it is not the empirical formula. The option CHO gives a hydrogen-to-carbon ratio of one, which contradicts the calculated ratio of two. The option C2H6O does not match the computed atom ratios at all and corresponds to a different composition such as ethanol. This mole-ratio procedure is exactly the NCERT method for empirical formulae. Plausibility check: the empirical formula must use the smallest integers, and CH2O satisfies the 1 : 2 : 1 ratio, confirming the answer.