The correct answer is (a) Uttarkashi.
Uttarkashi district has the largest forest cover out of total geographical area in Uttarakhand. The forest cover in Uttarkashi district is about 70% of the total geographical area. The main reason for this is that the district is located in the Himalayas, which is a mountainous region with a lot of forest cover. The forest cover in Uttarkashi district is important for a number of reasons. It helps to protect the environment, it provides a habitat for wildlife, and it helps to regulate the climate.
The other options are incorrect because they do not have the largest forest cover out of total geographical area in Uttarakhand. Chamoli district has a forest cover of about 60% of the total geographical area, Tehri Garhwal district has a forest cover of about 50% of the total geographical area, and Almora district has a forest cover of about 40% of the total geographical area.