The incorrect option is b.
Oral erythromycin is a macrolide antibiotic that is not recommended to treat acne. Topical clindamycin and oral minocycline and tetracycline are all considered effective treatments for moderate-to-severe acne, with oral versions of tetracycline and minocycline being the most commonly prescribed. Erythromycin is typically prescribed for other conditions, such as certain bacterial infections and inflammatory conditions. So it would not be the best choice in this situation, making option b the incorrect choice.