Question

what defines an estuary biome? only freshwater polluted water mix of salt & fresh water only saltwater

Explanation:

An estuary is a coastal area where freshwater from rivers and streams mixes with saltwater from the ocean. This mixing of waters creates a unique and dynamic ecosystem with specific characteristics. The other options are incorrect: "Only freshwater" would describe a river or lake, "Polluted water" is a general and negative description not specific to estuaries, and "Only saltwater" would be more characteristic of the open ocean.

Answer:

Mix of salt & fresh water