Final answer:
The maximum allowable limits for Dihydrocodeine to be classified as Schedule III are based on concentration and formulation, rather than a strict weight limit like the options provided. Therefore, the correct answer is 'None of the above'.
Step-by-step explanation:
The question pertains to the Schedule III classification for the drug Dihydrocodeine under the Controlled Substances Act in the United States. Schedule III drugs are substances that have a potential for abuse less than substances in Schedules I or II and abuse may lead to moderate or low physical dependence or high psychological dependence. The maximum allowable limits for a substance like Dihydrocodeine to be classified as a Schedule III substance are not strictly defined by a single quantity such as 5 grams, 10 grams, 15 grams, or 20 grams but are based on its formulation and other specific criteria, including concentration in combination with other substances. However, for drugs with codeine, one of the criteria for falling into Schedule III is if the preparation contains not more than 1.8 grams of codeine per 100 milliliters or not more than 90 milligrams per dosage unit, with an isoquinoline alkaloid of opium. Therefore, the provided options are incorrect, and the correct response is None of the above as the limits are specific to concentration and formulation rather than a total weight limit.