(b) Grass, goat and human constitute a food chain. Grass is an autotroph i.e. it produces its own food. Grass is eaten by goat which is a herbivore. Human beings are omnivores (they eat both meat and plant foods) so they eat meat of goat. Hence this is a food chain.

Grass → Goat → Human

(Producer) (Herbivore) (Omnivore)

The other options are not proper food chains.