Concept:Industrial zones vary by concentration of factories, infrastructure, and economic activity.Explanation:Lagos–Ikeja is Nigeria’s most industrialized zone.Port Harcourt–Aba is a major oil and manufacturing hub.Abeokuta–Ibadan also has significant industrial establishments.Lokoja–Ajaokuta, aside from the Ajaokuta steel plant, has far fewer industries.Therefore, it has the least industrial concentration among the listed zones.Answer:A. Lokoja – Ajaokuta