Select the incorrect food chain.

Grass → Frog → Vulture

The incorrect food chain is (a) Grass → Frog → Vulture.

In a typical food chain, frogs are indeed considered secondary consumers as they primarily feed on primary consumers, such as insects. Vultures, on the other hand, are tertiary consumers that consume secondary consumers .

Considering this information, the incorrect food chain is: (a) Grass → Frog → Vulture

This food chain suggests that vultures eat frogs, which is not a common feeding relationship observed in ecosystems.

The other food chains are correct. In (b), the grasshopper is a primary consumer, the frog is a secondary consumer, the snake is a tertiary consumer, and the eagle is a quaternary consumer. In (c), the deer is a primary consumer, the lion is a secondary consumer, and the man is a tertiary consumer. In (d), the phytoplankton are primary producers, the zooplankton are primary consumers, the perch are secondary consumers, the bass are tertiary consumers, and the man is a quaternary consumer.

So the answer is (a).