The correct answer is: A. Fish
Exotic trouts are a type of fish that are not native to Himachal Pradesh. They were introduced to the region in the early 1900s by British anglers. There are several different species of exotic trouts found in Himachal Pradesh, including brown trout, rainbow trout, and brook trout. These fish are popular among anglers and are considered to be a delicacy.
Option B, crab, is incorrect because crabs are not fish. They are crustaceans, which are a type of invertebrate.
Option C, prawn, is incorrect because prawns are also not fish. They are crustaceans, like crabs.
Option D, turtle, is incorrect because turtles are reptiles. They are not fish or crustaceans.