Which of the following statements about animals are true? A: amphibians are the only group of animals without any outer covering on their skin. B: birds are the only group of animals with an outer body covering of feathers. C: fish are the only group of animals with an outer body covering of scales. D: mammals are the only group of animals with an outer body covering of hair and suckle their young.

• A.  A and C only
• B.     B and D only
• C.     A, C and D only
• D.     B, C and D only