The strength of the organic acids and chloro substituted acids is measured by pKa scale such that smaller value of pKa corresponds to:

Explanation

Option A is correct. The strength of an organic acid is measured by its pKa value. The smaller the pKa value, the stronger the acid. The pKa scale is a measure of the acidity of a molecule. A lower pKa value means that the molecule is more acidic. In the case of organic acids, a lower pKa value means that the acid is more likely to donate a proton (H+). The reason why chloro substituted acids are stronger acids than their non-chlorinated counterparts is because the chlorine atoms withdraw electrons from the carbonyl group, making it more acidic. pKa∝1/acidity