Which of the following is responsible for the increased growth of algae in the dead zones?
choice a., elevated carbon and nitrogen in the water
choice b., elevated carbon and phosphorous in the water
choice c., elevated nitrogen and oxygen in the water
choice d., elevated phosphorous and nitrogen in the water
choice e., elevated phosphorous and oxygen in the water

Choice D., elevated phosphorous and nitrogen in the water

Explanation:

The dead zone is caused by the enrichment of nutrients from the river, especially nitrogen and phosphorus. Most of the nitrogen supply comes from the main agricultural states.  

Nitrates and phosphorus used in fertilizers have a key effect once they reach the river. They stimulate an explosive growth of algae, which when they die fall to the bottom of the sea and decompose.  

The bacteria that break down the algae consume oxygen, in a process that drastically reduces the level of gas available for marine life.