C

Anterior-lateral thigh, upper outer arm, and periumbilical abdomen are the routinely taught and studied sub-cutaneous insulin sites; the “dorsum of arm” (back of the forearm/hand) is not listed in standard recommendations and is seldom used in practice, making it the least preferred option [Smith 1991 PMID 1863105; Koivisto 1980 PMID 6444267].