Carboxylic Acids (Inductive Effects, Esterification)

Problem # 725

A chemist carried out a Fischer esterification using methanol that was isotopically labeled with 18O (indicated with an asterisk).

Which one of the esters below (A-D) was formed?

Problem # 724

Use curved arrows to show the formation of the tetrahedral intermediate of a Fischer esterification reaction (shown below). There are three steps in total.