The Multiple Nuclei Theory, proposed by Harris and Ullman in 1945, posits that cities develop around multiple centers (or nuclei), each serving different functions (e.g., commercial, industrial). Option A (Multiple Nuclei) matches this description. The APA’sAICP Certification Exam Content Outline(2022), under “Fundamental Planning Knowledge,” states, “Multiple Nuclei Theory describes urban form as organized around several discrete centers of activity.” Option B (Central Place Theory) focuses on the distribution of services, not urban form. Option C (Concentric Zones) describes a single-center model by Burgess. Option D (Sector Theory) emphasizes radial growth along transportation corridors. TheCPC Study Manual(2024) confirms, “Multiple Nuclei Theory explains urban form with multiple centers,” supporting option A.