Final answer:
The item that must not be on the specimen label is the diagnosis. Patient's name, date, and time of collection are required, but including the diagnosis is not standard protocol for labeling specimens in clinical settings.
Step-by-step explanation:
In a clinical setting, it is imperative that every specimen is correctly labeled to ensure accurate patient identification and to aid in providing the correct diagnosis and treatment. Of the options provided, the information that must not be on the specimen label is c. Diagnosis. The label should include the patient's name, the date and time of collection, but including the diagnosis on the specimen label is not standard practice as diagnoses can change and are not part of the specimen identification protocol.