Final answer:
Invertebrates that are generally small and can live on little food and hide from enemies are insects. They need less food to survive, reproduce quickly, and have physical adaptations that allow them to thrive in various environments, including evasion of predation.
Step-by-step explanation:
The invertebrates that are generally small, allowing them to live on little food and to hide from enemies, are insects (A). Invertebrates include a vast array of animals without a backbone, and among these, insects are particularly well-known for their small size. This diminutive stature enables them to require less food for survival, to reproduce rapidly, and to evade predators more effectively than larger animals.
Insects are the most numerous invertebrates on Earth, found in a range of habitats including soil, water, and air, thereby highlighting their adaptability. They exhibit diverse behaviors, with some capable of flight, a feature no other invertebrates possess, and this plays an integral role in their success as a group. Additionally, insects serve critical ecological functions, such as pollinating flowering plants and decomposing organic matter.
In summary, while some invertebrates like sponges have simplistic structures and live aquatic lifestyles, insects are diversified and remarkably successful due to their small size and versatility.