Final answer:
Saudi Arabia takes up most of the Arabian Peninsula, which is the world's largest peninsula. It is rich in oil resources, and also holds significant religious importance as the birthplace of Islam. The correct answer is A.
Step-by-step explanation:
The country that takes up most of the world's largest peninsula is Saudi Arabia. Known as the Arabian Peninsula, this region is characterized by its desert climate, notably the Rub' al-Khali or the 'Empty Quarter'—one of the largest sand deserts in the world. Saudi Arabia dominates the peninsula not only in terms of land area, but also with its vast oil resources which significantly contribute to its economy. While the region predominantly practices Islam, Saudi Arabia is especially significant because it is the birthplace of this religion, housing the holy cities of Medina and Mecca. The correct answer is A.