Characteristics of Estuaries

Which of the following statements about estuaries are true?

A. They serve as gateways to the freshwater breeding grounds of certain marine animals.

B. They provide breeding grounds for many types of aquatic animals.

C. Estuaries are resistant to pollution because the constant inflow of freshwater flushes pollutants into the ocean.

D. They are areas where freshwater streams or rivers merge with the sea.