The Alpine vegetation in the western Himalayas is found only up to a height of 3000 metres, while in the eastern Himalayas it is found up to a height of 4000 metres, The reason for this variation in the same mountain range is that

1. The question observes a difference in the upper limit of Alpine vegetation between the western Himalayas (around 3000m) and the eastern Himalayas (around 4000m) and asks for the reason. 2. Alpine vegetation (typically shrubs, meadows, stunted trees) occurs above the tree line, limited primarily by low temperatures. 3. The elevation limit for vegetation types (tree line, alpine zone) is influenced by temperature, precipitation, latitude, and aspect. 4. Comparing the western and eastern Himalayas: - (A) While overall peaks might differ, the general height difference doesn't directly explain the vegetation line variation. - (B) The eastern Himalayas are at a lower latitude (closer to the Equator) than the western Himalayas. Lower latitudes generally mean warmer temperatures at equivalent altitudes. Additionally, the eastern Himalayas are closer to the Bay of Bengal (sea coast), influencing moisture and temperature patterns. - (C) The eastern Himalayas generally receive significantly more monsoon rainfall than the western Himalayas. Higher precipitation, combined with warmer temperatures due to lower latitude and maritime influence, allows vegetation to survive at higher altitudes. - (D) Soil fertility (rocks) differences are unlikely to be the primary reason for such a large-scale difference in the alpine vegetation limit. 5. The combination of higher rainfall and warmer temperatures (due to lower latitude and proximity to the sea) in the eastern Himalayas allows the tree line and consequently the Alpine vegetation zone to extend to higher altitudes compared to the drier and relatively colder conditions at similar altitudes in the western Himalayas. Both B and C contribute, but higher monsoon rainfall (C) is often cited as a major factor alongside the temperature differences linked to latitude and maritime influence (B). Option C provides a strong direct reason related to climatic conditions.