Explanation:

- Option 1: Chankan Pass

- Not widely known for connecting Tawang with Lhasa.

- It is not commonly mentioned in this context.

- Option 2: Bum La Pass

- This is the pass that connects Tawang in Arunachal Pradesh, India, with Tibet (near Lhasa).

- Historically significant as part of the ancient trade route.

- Option 3: Hpungan Pass

- Not relevant to the Tawang-Lhasa connection.

- No notable relation to this corridor.

- Option 4: Kumjawng Pass

- This pass is not linked to Tawang and Lhasa.

- Not typically recognized in discussions about these areas.