Which one of the following statements is true? explain your answer.
a. when materials are subjected to a tensile stress, the laterial strain is always negative.
b. when metals are subjected to a tensile stress, the lateral strain is always positive.
c. when materials are subjected to a tensile strain, the laterial strain is always negative.
d. when metals are subjected to a tensile stress, the strain is always proportional to the magnitude of the stress.
e. when materials are subjected to a compressive stress, the young's modulus is always positive.