The correct answer is A. Hajj
Step-by-step explanation:
In the image, thousands of Muslims visit the Kaaba, which is an important religious building located in Mecca. This building is the black building in the center. Moreover, this important practice is part of the hajj or Islamic pilgrimage because in Islam religion believers are encouraged to visit Mecca in Saudi Arabia at least once during their life. Additionally, visiting the Kaaba is part of the hajj as this building is considered to be the "House of God".