The correct answer is A. Una.
Una district has the highest SCs male literacy rate in Himachal Pradesh. According to the 2011 census, the SCs male literacy rate in Una district is 87.6%. This is higher than the state average of 82.8%.
The other options are incorrect because they have lower SCs male literacy rates than Una district. For example, the SCs male literacy rate in Hamirpur district is 82.4%, the SCs male literacy rate in Kangra district is 82.3%, and the SCs male literacy rate in Chamba district is 81.9%.
The SCs male literacy rate is an important indicator of the social and economic development of a district. A high SCs male literacy rate indicates that the district has a well-educated population, which is essential for economic growth.