Concept:Abu Dawud was a famous compiler of Hadith. His birthplace is a key biographical fact.Explanation:Abu Dawud, the renowned Hadith collector, was born in the region known as Sidjistan (Sistan).This area lies in the eastern part of the Islamic world, not in Balkh, Basra, or Bukhara.His full name links him to this region, confirming his origin.Answer:D. Sidjistan