What are the organisms that feed on plant sap and other plant parts called?

Which of the following can be truly considered a parasite?

Sometimes parasites themselves are parasitised by other organisms. Such parasites are known as:

Assertion : Animals adopt different strategies to survive in hostile environments.
Reason : Praying mantis is green in colour which merges with plant foliage.

Brood parasitism is observed in which of the following?

Animals eating plants are categorised separately as $A$,they are in a broad ecological context,not very different from $B$. Choose the correct option for $A$ and $B$.