Final answer:
The definitions for the terms are matched as follows: Headwaters are the source of a river, a Lentic ecosystem is a body of still water, an Ecotone is the border between two biomes, and Eutrophication is the richness of nutrients in water.
Step-by-step explanation:
In order to match each term with its proper definition for a student who is seeking help with this particular task, we would arrange them as follows:
- Headwaters - A) The beginning and source of the river
- Lentic ecosystem - D) Formed by a body of standing or still water
- Ecotone - C) The border between two biomes
- Eutrophication - B) Excessive richness of nutrients in a body of water
Each of these terms describes a different aspect of freshwater biomes and ecosystems, ranging from the physical geography of rivers and streams to the ecological processes that affect bodies of water.