which starting material on heating with concentrated sulfuric acid generate cyclic ester I have just learned esterification of normal reactions with aliphatic compounds, but this one is a cyclic compound. Is it different? There are both a hydroxyl group and a carboxyl group in choice B and D, but why the correct answer is B, not D?
The correct answer is glycolic acid, B.

It forms the cyclic di-ester glycolide (1,4-dioxane-2,5-dione).