For which one of the following snakes is the diet mainly composed of other snakes, making it an example of a specialised snake eating predator?

Introduction / Context:
Diet and feeding behaviour are key aspects of animal ecology. Most snakes feed on small mammals, birds, or amphibians, but some species are specialised predators of other snakes. Such snake eating snakes are called ophiophagous. This question asks which of the listed snake species is particularly known for having a diet that mainly consists of other snakes.

Given Data / Assumptions:

• The focus is on diet composition, not merely occasional predation.
• The options list Krait, Russell's viper, Rattlesnake, King cobra, and Rat snake.
• One of these snakes is widely recognised as an ophiophagous predator of other snakes.
• While other species may occasionally eat snakes, only one relies heavily on them as primary prey.

Concept / Approach:
The King cobra is famous as a snake eating snake. Its scientific name Ophiophagus hannah literally means snake eater. King cobras commonly prey on smaller snakes, including venomous species, and may also consume lizards and other animals but have a strong preference for snake prey. Kraits and some other snakes may consume snakes occasionally, but they are not so specialised. Therefore, in a general knowledge context, the King cobra is the classic example of a snake whose diet mainly consists of other snakes.

Step-by-Step Solution:
Step 1: Recall which snake species is popularly associated with eating other snakes as its main food.Step 2: Recognise that the scientific name of King cobra, Ophiophagus hannah, directly refers to snake eating behaviour.Step 3: Note that Kraits, vipers, rattlesnakes, and rat snakes mostly eat rodents, frogs, or other small animals, though they may sometimes take snakes.Step 4: Because King cobra relies heavily on snakes as its principal prey, it stands out as the specialised ophiophagous snake.Step 5: Choose King cobra as the correct answer.

Verification / Alternative check:
Herpetology references and wildlife documentaries frequently highlight King cobra's diet, showing it hunting and consuming other snakes. Its scientific name and field observations confirm this behaviour. While a few other snakes occasionally eat their own kind or other species, none in the options is as strongly identified with a snake based diet as the King cobra. This evidence confirms that King cobra is the best and accepted answer.

Why Other Options Are Wrong:
Option A: Krait may sometimes eat snakes but primarily preys on small vertebrates like rodents and other animals.Option B: Russell's viper mainly eats rodents and small mammals, not mainly other snakes.Option C: Rattlesnakes generally feed on rodents and birds rather than specialising in snake prey.Option E: Rat snakes are rodent eaters and are often useful for controlling rats in agricultural areas.

Common Pitfalls:
Students may confuse occasional snake eating behaviour with a primarily snake based diet. Another error is assuming that any large venomous snake is automatically specialised in eating other snakes. To avoid such mistakes, remember that the King cobra's very name and reputation emphasise its ophiophagous lifestyle, making it the correct choice here.

Final Answer:
The correct answer is King cobra.