Explanation

Option A is correct because the Prophet Muhammad (PBUH) is the final prophet to whom Islam was revealed. Option B is incorrect because Hazrat Ibrahim (A.S) is a revered prophet but not the one who founded the specific Ummah referred to in this context. Option C is incorrect because Hazrat Ismaeel (A.S) is another important prophet, but not the primary focus for belonging of the Muslim Ummah. Option D is incorrect because Hazrat Yaqoob (A.S) is a respected prophet, but not the one defining the current Muslim Ummah.