As we know that if there is more solar insolation, there will be more temperature which in turn favourable for vegetation. So, at equator the intensity of sunlight is more which favours for more dense vegetation(tropical evergreen forests). As going to higher latitudes the intensity of sunlight decreases, so the vegetation type also changes from tropical to subtropical, temperate and then to sub-polar, tundra type.
Coming to the question,
1. In Himalayan region: it is far from equator, so the temperature decreases which means the type of vegetation to change.
2. As we know that the temperature reduces by 1degree for every 165 metres rise in height. So, at 915 metres the temperature is relatively very low, which ultimately leads to change the vegetation type to subtropical and montane vegetation.

Hope this will be helpful,
If any mistakes please correct.

The vegetation on the slopes of the Himalayas and the hills of the peninsula changes from tropical to subtropical, temperate, and alpine vegetation due to a fall in temperature.

Impact of temperature on vegetation distribution:
- Temperature plays a crucial role in determining the type of vegetation that can survive in a particular area. Different plants have different temperature requirements for growth and survival.
- As we move from the tropical regions towards higher altitudes, the temperature gradually decreases. This decrease in temperature influences the types of plants that can thrive in those areas.

Explanation of the answer:
- The correct answer to the given question is option 'C', which states that the change in vegetation is due to a fall in temperature.
- This is because as we move to higher altitudes, the temperature drops significantly. The drop in temperature creates a hostile environment for tropical vegetation, which is adapted to warmer climates.
- The fall in temperature makes it difficult for tropical plants to survive, and they are gradually replaced by plants that are adapted to cooler temperatures.
- As we ascend the slopes of the Himalayas and the hills of the peninsula, the vegetation changes from tropical to subtropical, temperate, and finally alpine vegetation.
- Subtropical vegetation is characterized by deciduous forests, which can tolerate cooler temperatures compared to tropical forests.
- Temperate vegetation includes coniferous forests, which are adapted to colder climates and have needle-like leaves to reduce water loss.
- Alpine vegetation consists of low-growing shrubs, grasses, and mosses that can survive in extremely cold and harsh conditions.
- This transition in vegetation types is primarily driven by the decrease in temperature with increasing altitude.

Other factors influencing vegetation distribution:
While temperature is the primary factor influencing the change in vegetation, other factors such as soil, high humidity, and very heavy rainfall also play a role in determining the specific vegetation types in different regions. However, in this particular question, the fall in temperature is the main reason for the change in vegetation from tropical to subtropical, temperate, and alpine.