Concept:The ruler who transferred the Omani capital to Zanzibar in the 19th century is Sa'id bin Sultan.Explanation:Sa'id bin Sultan ruled Oman from 1806 to 1856.He developed strong commercial ties with East Africa, especially Zanzibar.He moved his capital from Muscat to Zanzibar around 1840 to focus on the clove trade and Indian Ocean commerce.Thus, the correct answer is option B.Answer:B. Sa'id bin Sultan