What does infestation refer to?

Infestation refers to a situation where a large number of pests, such as insects or rodents, occupy an area and often lead to damage, contamination, or other adverse effects. This term is commonly used to describe scenarios where the population of these pests exceeds what is considered normal or manageable, resulting in health risks or property damage.

In the context of this question, the idea of "a large number of animals causing damage" accurately captures the essence of infestation. An infestation indicates not just the presence of these pests but also their overwhelming numbers and the potential harmful impact they have on both health and environment.

The other options do not reflect the true meaning of infestation. For instance, mentioning harmless insects suggests there's no threat, while the absence of insects contradicts the concept of infestation altogether. Similarly, a controlled number of pests implies management rather than infestation, which involves an uncontrolled or overwhelming presence.