Concept:Iʿtikāf is a spiritual retreat in the mosque, mainly during the last ten days of Ramadan.
Explanation:The main purpose of Iʿtikāf is to devote oneself fully to worship.
It is especially observed in the last ten days of Ramadan.
During this period, Muslims seek Laylat al-Qadr, the Night of Power.
This night is better than a thousand months.
Therefore, the essence of Iʿtikāf is to gain the blessings of the Night of Power.
Answer:C. Derive benefit from the night of power.