Final answer:
To be classified as Schedule III, hydrocodone products must contain no more than 15 milligrams of hydrocodone per dosage unit. The maximum allowable limit for hydrocodone to be classified as Schedule III is 10 milligrams. Therefore, the correct option is 4.
Step-by-step explanation:
The maximum allowable limit for hydrocodone to be classified as Schedule III, according to the Drug Enforcement Administration (DEA), is 15 milligrams per dosage unit. Hydrocodone combination products exceeding this limit are classified as Schedule II substances.
Therefore, among the provided options, 10 milligrams falls within the acceptable range for Schedule III classification.
Therefore, the correct option is 4.