Answer:
A
Step-by-step explanation:
B, C, and D are examples of single species on Earth, while A is not.
Option B refers to all the water lilies in a pond, which is a single species of plant.
Option C refers to all the bullfrogs in a pond, which is a single species of amphibian.
Option D refers to all the small mouth bass in a pond, which is a single species of fish.
Option A, however, refers to all the bacteria in a pond. Bacteria are a diverse group of microorganisms, and a pond can contain many different species of bacteria, making option A not an example of a single species on Earth.Therefore, the correct answer is A.