Q: What organism constitutes frothy green "pond scum"?


Read this paragraph and choose the correct option from the provided answers:

Polluted water can form a frothy green scum on the surface. This "pond scum" is actually a living organism, algae. The algae are plant-like protists. Usually the algae are too small to notice, but sometimes algae grow in excess because of the excess nutrients in polluted water.

 Choices:

- bacteria

- sponges

- protozoa

- algae


A:
algae