For which one of the following venomous snakes is the natural diet mainly composed of other snakes (an ophiophagous feeding habit)?

Introduction:
Some snakes specialise in eating other snakes, a behaviour known as ophiophagy. This question checks your awareness of this special feeding habit and asks which of the listed venomous snakes has a diet that mainly consists of other snakes in the wild.

Given Data / Assumptions:
- Options include rattlesnake, king cobra, krait and Russell's viper. - All listed species are venomous snakes found in different regions. - The question focuses on normal diet in nature, not rare or captive behaviour. - We assume standard zoology classification and common field observations.

Concept / Approach:
The key concept is ophiophagy, which means a diet that consists largely of other snakes. While many snakes may occasionally eat other reptiles, only a few rely mostly on snakes as prey. The king cobra is especially famous as a snake eater, preying on other cobras, kraits and various snakes in forests. Therefore, recognising this behavioural trait of the king cobra leads to the correct answer.

Step-by-Step Solution:
Step 1: Recall which snakes are widely known as snake eaters from basic zoology and general knowledge. Step 2: Remember that the king cobra is often described as ophiophagous and hunts other snakes as its primary food. Step 3: Compare this with the rattlesnake, krait and Russell's viper, which mainly feed on rodents, small mammals, and sometimes birds or amphibians. Step 4: Conclude that the king cobra best matches the description of a snake whose diet is mainly composed of other snakes.

Verification / Alternative check:
Standard herpetology references describe the king cobra as feeding largely on other snakes, including venomous species such as kraits and other cobras. This unique behaviour is so prominent that it is often mentioned in school level general knowledge books, further confirming that king cobra is the correct choice.

Why Other Options Are Wrong:
Rattlesnake: Typically preys on rodents, small mammals and small birds, not mainly on snakes. Krait: Although venomous and dangerous, kraits usually hunt small vertebrates like rodents and frogs; they are not primarily snake eaters. Russell's viper: Hunts rodents, lizards and other small animals; it is not characterised by a diet of snakes.

Common Pitfalls:
Learners sometimes choose krait or Russell's viper because these are well known and dangerous, assuming that a powerful venom automatically implies that the snake hunts other snakes. However, diet and venom potency are separate issues. Focusing on the behavioural keyword ophiophagous helps to correctly link it with the king cobra.

Final Answer:
The snake whose natural diet is mainly composed of other snakes is the King Cobra.