Option 1: Assam -> The Brahmaputra flows through Assam extensively, but this is not where it enters India.
Option 2: Arunachal Pradesh -> The river enters India through this northeastern state from Tibet.
Option 3: Sikkim -> Located in a different region; the Brahmaputra does not pass through Sikkim.
Option 4: Meghalaya -> Situated south of the Brahmaputra's course; not the entry point.
Hence, Option 2: Arunachal Pradesh -> The Brahmaputra river, known as Yarlung Tsangpo in Tibet, enters India through Arunachal Pradesh where it is called Siang or Dihang. It then flows westward through Assam before entering Bangladesh -> correct