Which of the following groups do not constitute a food chain ? (i) Wolf, rabbit, grass, lion (ii) Plankton, man, grasshopper, fish (iii) Hawk, grass, snake, grasshopper, frog (iv) Grass, snake, wolf, tiger

The groups that do not constitute a food chain are (i) Wolf, rabbit, grass, lion and (iv) Grass, snake, wolf, tiger. A food chain is a linear sequence of organisms that eat other organisms as a source of food and energy. In a food chain, each organism is eaten by only one other organism. In the given groups, (i) and (iv) do not follow this rule.