Christo is working to restore oyster populations along coastal regions in the United States. Which of the following statements BEST describes why oysters are struggling in these waters?
A. Concentrated oxygen has caused fewer carbonate ions to build shells.
B. Pesticides from runoff have caused fewer carbonate ions to build shells.
C. Ozone layer protections have caused fewer carbonate ions to build shells.
D. Increased water acidity has caused fewer carbonate ions to build shells.