Choor Chandni or Churdhar (3647 m) mountain range falls in the district of

Sirmaur
Chamba
Kangra
Kullu

The correct answer is: A. Sirmaur

Choor Chandni or Churdhar (3647 m) is a mountain range in the Sirmaur district of Himachal Pradesh, India. It is a popular tourist destination and is known for its scenic beauty. The mountain range is also home to a number of temples and shrines.

Option B, Chamba, is incorrect because the Churdhar mountain range is located in the Sirmaur district, not the Chamba district.

Option C, Kangra, is incorrect because the Churdhar mountain range is located in the Sirmaur district, not the Kangra district.

Option D, Kullu, is incorrect because the Churdhar mountain range is located in the Sirmaur district, not the Kullu district.