Which of the following statements about species,as defined by the biological species concept, is (are) correct?
I. Biological species are defined by reproductive isolation
II. Biological species are the model used for grouping extinctforms of life
III. The biological species is the largest unit of population inwhich successful reproduction is possible
Choose one answer.
    a. Ionly    
    b. IIonly    
    c. I andIII    
    d. II andIII    
    e. I, II, andIII