Option 1 -> Tripura, Manipur, and Mizoram are northeastern states but none of them share a border with Bhutan.
Option 2 -> Assam and Arunachal Pradesh share borders with Bhutan, but Mizoram does not.
Option 3 -> Sikkim and Assam share borders with Bhutan, but Manipur does not.
Option 4 -> All three states—Sikkim, Assam, and Arunachal Pradesh—share land borders with Bhutan.
Hence, Option 4: Sikkim, Assam, Arunachal Pradesh -> Four Indian states share borders with Bhutan: Sikkim, West Bengal, Assam, and Arunachal Pradesh. Among the given options, only Option 4 correctly lists states that all share borders with Bhutan -> correct