Explanation

D is correct because Hazrat Abu Bakar (R.A.) was the first Caliph after the Prophet Muhammad (PBUH). A is incorrect because Hazrat Ali (R.A.) was the fourth Caliph. C is incorrect because Hazrat Usman (R.A.) was the third Caliph. B is incorrect because Hazrat Umar (R.A.) was the second Caliph.