The correct answer is option 'D', which states that the physiographic region located in the southern part of India is the Western Ghats. Let's explore this answer in detail:

Western Ghats:
- The Western Ghats, also known as the Sahyadri Mountains, are a mountain range that runs parallel to the western coast of the Indian peninsula.
- It is one of the eight hotspots of biological diversity in the world and is recognized as a UNESCO World Heritage Site.
- The Western Ghats cover a distance of about 1,600 km and extend through the states of Gujarat, Maharashtra, Goa, Karnataka, Kerala, and Tamil Nadu.
- These mountains act as a physical barrier and separate the Deccan Plateau from the coastal plains of the Arabian Sea.
- The Western Ghats are known for their rich biodiversity, with numerous endemic species of plants, animals, and birds.
- The region receives heavy rainfall due to the southwest monsoon, resulting in the formation of several rivers, waterfalls, and lush green forests.

Other Options:
a) Himalayan Mountain Range:
- The Himalayan Mountain Range is located in the northern part of India, spanning across several states such as Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, and Arunachal Pradesh.
- It is the highest mountain range in the world and includes some of the highest peaks like Mount Everest and Kanchenjunga.

b) Indian Peninsula:
- The Indian Peninsula refers to the southern part of the Indian subcontinent, surrounded by the Arabian Sea in the west, the Bay of Bengal in the east, and the Indian Ocean in the south.
- It consists of several physiographic features such as plains, plateaus, hills, and coastal regions.

c) Karakoram Mountain Range:
- The Karakoram Mountain Range is located in the northern part of the Indian subcontinent, mostly in the region of Gilgit-Baltistan in Pakistan-administered Kashmir and Ladakh in India.
- It is one of the highest mountain ranges in the world and includes the second-highest peak, K2.

In conclusion, the physiographic region located in the southern part of India is the Western Ghats, known for its biodiversity, scenic beauty, and the role it plays in the hydrology of the region.