Which among the following is the incorrect food chain?

Grass-> Grasshopper-> Frog-> Snake-> Eagle. Phytoplanktons-> Zooplanktons -> Small Fish-> Large Fish. Diatoms-> Zooplanktons-> Small Fish. Grass->Frog->Vulture.

Grass->Frog->Vulture.

Frog is the secondary consumer, i.e., it feeds upon herbivore in a particular food chain but in the given food chain it is acting as a primary consumer hence, the given food chain is incorrect.