Correct Option: D

The compounds that resist biodegradation and thereby persist in the environment are called recalcitrant. The recalcitrant xenobiotic compounds can be grouped into the following six types:
(i) halocarbons;
(ii) polychlorinated biphenyls;
(iii) synthetic polymers;
(iv) alkylbenzyl sulphonates;
(v) oil mixture and
(vi) others.