ANS:D - -0.24

The Poisson's ratio (ν) relates the lateral strain (εlateral​) to the longitudinal strain (εlongitudinal​) in a material under uniaxial tension. It is given by the formula: ν=−​εlateral​​/εlongitudina Given that the Poisson's ratio (ν) is 0.3 and the longitudinal strain (longitudinal​) is 0.8, we can use the formula to find the lateral strain (εlateral​): 0.3=−0.8εlateral​​ εlateral​=−0.3×0.8 εlateral​=−0.24 Therefore, the magnitude of the thickness strain is -0.24. So, the correct option is: −0.24