Explanation:

- Option 1: Duars

The Duars are the floodplains and foothills on the southern side of the eastern Himalayas in West Bengal and Assam. They are part of the Terai-Duar savanna and grasslands.

- Option 2: Tehri

Tehri is a district in Uttarakhand, known for the Tehri Dam. It is not a valley between mountain ranges like the Lesser Himalayas and Shivaliks.

- Option 3: Terai

The Terai is a lowland region south of the Shivalik Hills. It is characterized by marshy grasslands and savannas.

- Option 4: Duns

The Duns are valley-like formations between the Lesser Himalayas and the Shivalik Hills. Examples include Dehradun and Kotli Dun.