What is the man regarded as in the food chain operating in an ecosystem?

With regard to various food chains operating in an ecosystem, man is a consumer. Consumers are all organisms dependent on plants and other organisms for food. There are three types of consumers.  

Primary consumers are those who eat plants.  

Secondary consumers are predators who eat meat. 

Tertiary consumers are top predators who feed on secondary consumers.  

Hence, the correct option is (a) Consumer.