The Khulafā al-Rāshidūn were the first four caliphs who ruled the Islamic state after the death of Prophet Muhammad (S.A.W). They were Abu Bakr, Umar, Uthman, and Ali (may Allah be pleased with them). They reigned between A.D. 632 and 661, which means that they ruled the Islamic state for approximately 29 years. Therefore, the correct answer is the first option: A.D. 632 and 661.