Which element is closely associated with the field of organic chemistry?

Carbon

Explanation:

The field of organic chemistry is the field  of the study of the compounds of carbon mostly with hydrogen but they  can contain the presence of other atoms such as oxygen, nitrogen, sulfur even metals such as lithium. It studies the structure, properties, synthesis and reactions of these compounds. The field of organic chemistry is the field of living organisms as they are mostly are formed by organic compounds hence its name organic.

the answer to this question is 3.