Answer the following question given this paragraph: 

Ester molecules are polar but have no hydrogen atom attached directly to an oxygen atom. They are therefore incapable of engaging in intermolecular hydrogen bonding with one another and thus have considerably lower boiling points than their isomeric carboxylic acids counterparts. Because ester molecules can engage in hydrogen bonding with water molecules, however, esters of low molar mass are somewhat soluble in water. Borderline solubility occurs in those molecules that have three to five carbon atoms. http://catalog. flatworldknowledge. com/bookhub/reader/2547 - gob-ch15_s07_t01lists the physical properties of some common esters.


Q: Lack of which attachment makes ester molecules incapable of intermolecular hydrogen bonding?

 Choices:

- carbon fluorine atom

- carbon sulfur atom

- carbon oxygen atom

- hydrogen-oxygen atom

A:
hydrogen-oxygen atom
