The correct answer is: A. fresh
A pond is a small body of water that is typically surrounded by land. It is a good example of a fresh water ecosystem because it contains water that is not salty. The water in a pond can be either still or flowing, and it can be home to a variety of plants and animals.
A brackish water ecosystem is a type of water ecosystem that contains a mixture of fresh water and salt water. Brackish water ecosystems are found in coastal areas, where rivers meet the ocean. The water in a brackish water ecosystem is typically less salty than ocean water, but more salty than fresh water.
A marine water ecosystem is a type of water ecosystem that contains salt water. Marine water ecosystems are found in oceans, seas, and other large bodies of water. The water in a marine water ecosystem is typically very salty.
A sea is a large body of salt water that is connected to an ocean. Seas are typically smaller than oceans, and they may be partially enclosed by land. The water in a sea is typically salty.