The correct answer is: a) Shirui Hills.
The Shirui Hills are a mountain range in the state of Manipur, India. They are located in the southern part of the state, and are part of the Indo-Burma ranges. The highest peak in the Shirui Hills is Mount Shirui, which is 2,650 meters (8,700 feet) tall.
The Shirui Hills are known for their prehistoric cave sites. These caves contain evidence of human habitation dating back to the Stone Age. The caves are also home to a variety of plant and animal life, including the endangered Shirui Lily.
The Shirui Hills are a popular tourist destination. The area is known for its beautiful scenery, its rich history, and its unique wildlife.
The other options are incorrect because:
- b) Nongmaiching Hills are not known for their prehistoric cave sites.
- c) Thangjing Hills are not known for their prehistoric cave sites.
- d) Koubru Hills are not known for their prehistoric cave sites.