Correct Option (a):
Oak and Rhododendron are naturally found in the Himalayan region.
- Oak (Quercus species) trees are characteristic of temperate forests across the Western and Eastern Himalayas, including states like Uttarakhand, Himachal Pradesh, and Sikkim.
- Rhododendron species are prominent plants in the Himalayan moist temperate and alpine zones. They are widely distributed in areas such as Sikkim, Arunachal Pradesh, and Uttarakhand.
Incorrect Options:
- Sandalwood (Santalum album) is primarily native to the dry deciduous forests of Southern India, particularly states like Karnataka, Tamil Nadu, and Andhra Pradesh. It does not grow naturally in the Himalayan ecosystem. Therefore, option 3 is incorrect, making options 2, 3, and 4 incorrect.