Identify the food chain in which the organisms of the second trophic level are missing :

In a food chain, the first trophic level consists of producers (like grass). The second trophic level consists of primary consumers or herbivores (like goats or grasshoppers). The third level consists of secondary consumers (small carnivores like frogs). In option (c): 'Tiger, grass, snake, frog', we have the producer (grass), but there is no herbivore (second trophic level) to eat the grass and be eaten by the frog. In contrast: (a) has a goat (2nd level), (b) has zooplankton (2nd level), and (d) has a grasshopper (2nd level).