Concept:Imam an-Nasai is best known for spending the major part of his life in the region of Khurasan.
Explanation:Imam an-Nasai, whose full name is Ahmad ibn Shu'ayb al-Nasa'i, was one of the great scholars of Hadith.
His name "an-Nasai" is derived from Nasa, a city located in the region of Khurasan, in present-day Turkmenistan.
He was born and raised there, and Khurasan remained his main base.
He later travelled to centers of learning such as Bukhara, Baghdad, and Egypt to collect Hadith.
Nevertheless, he spent most of his daily life and scholarly activity in Khurasan.
It was there that he studied, taught, and compiled his renowned collection known as the Sunan an-Nasa'i.
This close connection with Khurasan is why he is counted among the great scholars of that region.
Answer:Imam an-Nasai spent his days in Khurasan, so the correct option is C.