PLEASE HELP ASAP.
The Fish and Wildlife Commission is conducting research on fish populations in one of the nation's largest rivers. According to the research, fish numbers are steadily declining each year. If the scientists want to better understand what is happening to the fish, what measurement would yield the best data?

A. opinions from local fishermen

B. dissolved oxygen in the water

C. the length of the river

D. fish population data from the nearest lake

Option B. dissolved oxygen in the water.

Explanation:

Oxygen molecule is important for land as well as aquatic organisms. This oxygen is very important for the survival of organisms because every living organisms needs oxygen for their growth and development. Optimum level of oxygen in water is 6.5-8 mg/Litre. If this concentration decrease or increase from optimum level, it causes death of marine animals.

The amount of dissolved oxygen in water plays a big role in fish population research.

Explanation:

Numerous scientific studies suggest that 4-5 parts per million of dissolved oxygen is the minimum amount that will support a large, diverse fish population. If the amount is getting smaller, it could explain why the population is in decline.

thats not even an aswer choice

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%