Which element provides strength to the exoskeletons of clams and oysters? sulfur oxygen hydrogen phosphorus

the national environmental policy act (nepa) is a united states environmental law that promotes the enhancement of the environment and established the president's council on environmental quality (ceq). the law was enacted on january 1, 1970. to date, more than 100 nations around the world have enacted national environmental policies modeled after nepa.

the answer is d.) homologous; have mammary glands