In this wetlands ecosystem, the is/are an important abiotic factor that could limit the underwater organism populations. a) dissolved oxygen b) number of predators c) number of plant species d) migratory bird population

A). dissolved oxygen    

Dissolved oxygen is the abiotic factor. Abiotic factors are the non-living components of the environment which can have an influence on the living organisms. Abiotic factors include soil, water, oxygen, temperature etc.

The underwater organism population gets oxygen from aquatic plants which produce oxygen by the process of photosynthesis. Therefore, oxygen is available in the dissolved state in water called as dissolved oxygen. Respiration by underwater animals and plants , decomposition and other chemical reactions requires oxygen. Utilization of dissolved oxygen by underwater animals can limit the overall concentration of dissolved oxygen which can affect the vital metabolism of underwater animals and therefore can limit their population.

sorry to break it to ya but no one can answer your question it's just

jk but i am serious about the part that most people cant answer it beacuse you did not mention the section you are talking about. but it would if you added some detail and were a bit more specific.

yes, because even though a theory has a  lot of evidence to support it, it is not always true