The correct answer is (b) Atkinson.
The book Himalayan Districts was written by William Edward Atkinson in 1882. It is a comprehensive history of the Himalayan districts of British India. The book is divided into two volumes, the first of which covers the districts of Kumaon and Garhwal, and the second of which covers the districts of Sikkim, Bhutan, and Nepal.
Atkinson was a British civil servant who served in India for many years. He was a keen observer of Indian society and culture, and his book is a valuable source of information on the history and geography of the Himalayan region.
The other options are incorrect.
(a) Gardner is the name of a British explorer who traveled to the Himalayas in the 19th century. He wrote a book about his travels, but it is not called Himalayan Districts.
(c) Shekhar Pathak is an Indian author who has written several books on the Himalayas. However, he did not write the book Himalayan Districts.
(d) Maula Ram is an Indian politician who has served as a member of the Indian Parliament. He is not the author of the book Himalayan Districts.