The correct answer is A. U. S. Parmar.
A. U. S. Parmar was an Indian historian and writer. He was born in 1914 in the village of Banjar in the Kullu district of Himachal Pradesh. He studied at the University of Punjab and the University of London. He was a professor of history at the Panjab University in Chandigarh. He was also the director of the Himachal Pradesh State Archives. He wrote several books on the history and culture of Himachal Pradesh. The book ‘Himalayan District of Kullu and Lahaul and Spiti’ is one of his most famous works.
B. Akshar Singh is a contemporary Indian writer. He is known for his novels and short stories. He has written several books on the history and culture of Himachal Pradesh. However, he did not write the book ‘Himalayan District of Kullu and Lahaul and Spiti’.
C. R. K. Kaushal is an Indian historian and writer. He is known for his books on the history of India. He has written several books on the history of Himachal Pradesh. However, he did not write the book ‘Himalayan District of Kullu and Lahaul and Spiti’.
D. A. P. F. Harcourt was a British historian and writer. He was known for his books on the history of India. He has written several books on the history of Himachal Pradesh. However, he did not write the book ‘Himalayan District of Kullu and Lahaul and Spiti’.