Final answer:
On the DD Form 1920, the suspect's Blood Alcohol Concentration (B.A.C.) should be recorded in Section IV, block 7c, which is designated for the results of chemical tests.
Step-by-step explanation:
The DD Form 1920, also known as the Alcohol Influence Report, is a document used by military authorities to record details of an incident involving alcohol use by military personnel. The suspect's Blood Alcohol Concentration (B.A.C.) should be recorded in Section IV, block 7c of the DD Form 1920. This part of the form specifically asks for the results of chemical tests, and that is where the B.A.C. readings obtained from breath, blood, or urine tests are to be entered. It is important for the official completing the form to ensure that this information is accurate and corresponds to the results provided from the tests conducted.