Extracted text: Problem12. Metallic rod of 500mm length and 50mm diameter, when subjected to a tensile force of 100kN at the ends, experiences an increase in its length by 0.5mm and a reduction in its diameter by 0.015mm. The Poisson's ratio of the rod material is_ А. 0.4 В. О.3 С. 0.5 D. 0.2