A material behaves in certain ways above and below the proportional limit on a stress strin curve, which of the following is correct______________?

A. Above the proportional limit a material function in a plastic manner, while below the proportional limit it behaves as an elastic
B. Above the proportional limit a material functions in an elastic manner, while below the proportional limit it behaves as an plastic
C. Either A or B
D. Neither A or B