What is each level of consumption in a food chain called?

The correct answer is trophic level.

Feeding relationship of different organisms in which one is being eaten by other is called food chain. Each group of organisms in a food chain is called trophic level.  Green plants are producers which make their food with the help of sun energy is included in one trophic level. Similarly plant eaters or herbivores are primary consumers and those animals which feed on primary consumers are secondary or tertiary or top consumers are other trophic levels.  

the answer is d.) homologous; have mammary glands