What is the term used to describe all animals that rely on plants, either directly or indirectly, for their food?

Consumers

The correct answer is (c) consumers.

All animals that rely on plants, either directly or indirectly, for their food needs are classified as consumers. Consumers obtain their energy and nutrients by consuming other organisms, including plants or other animals in the food chain.

Option (a) decomposers refers to organisms that break down dead organic matter into simpler inorganic substances.

Option (b) root feeders specifically feed on plant roots.

Option (d) grazers are animals that primarily consume grass or vegetation by grazing.

Therefore, the most suitable choice is (c) consumers, as it encompasses all animals that depend on plants for their food, whether directly by consuming plants or indirectly by consuming other animals that rely on plants as their food source.