Which of the following constitute a food-chain?
a. Grass, wheat and mango
b. Grass, goat and human
c. Goat, cow and elephant
d. Grass, fish and goat

In the option,

(b) Grass, goat and human

Grass acts as the producer

Goat acts as the primary consumer

Man acts as the secondary consumer

Hence, option (b) constitutes a food chain.