Final answer:
Command Directed Testing is the protocol used when a commander orders a drug or alcohol test for soldiers returning from temporary duty without any suspicion of substance abuse. The correct option is C.
Step-by-step explanation:
When soldiers return from temporary duty and are asked to be tested by a commander, the correct code used is Command Directed Testing. This protocol is employed when a commanding officer orders a drug or alcohol test without any suspicion of substance abuse. It is a standard procedure following certain events, such as returning from temporary duty, an accident, or other situations where testing is deemed necessary by command. The correct option is C.