Answer:
A. Egrets eat insects that are unearthed after livestock graze, but do not affect the livestock
Explanation:
Commensalism is a type of biological interaction where the members of one species obtain a benefit, while members of another species neither benefit nor suffer from the interaction. On the other hand, amensalism is a relationship where one species is harmed while the other remains unaffected. In this example, Egrets are benefited because they obtain insects that can eat, while livestock is unaffected, thereby it is a case of commensalism.