The correct answer is D. Devanagari.
Devanagari is a writing system that originated in India and is used to write several languages, including Hindi, Marathi, and Nepali. It is also the official script of India.
Tankari is a writing system that was used in Himachal Pradesh in the past. It is no longer in use.
Persian is a writing system that is used to write the Persian language. It is not widely used in Himachal Pradesh.
Kului is a writing system that is used to write the Kului language. It is not widely used in Himachal Pradesh.
Devanagari is the most popular script in Himachal Pradesh today because it is the official script of India and is used to write several languages that are spoken in the state.