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I answered D. It said it was wrong. Show the correct solution for this problem. The current density, J, of a material is proportional to to the electric field, E. subjected into the material. What is the proportionality constant referred to? A. surface charge density B. conductivity C. Coulomb's constant D. resistivity I answered A. It said it was wrong. Show the correct solution for this problem. A book is placed on a table. Then an apple is placed on the book. The table exerts a normal force A. on both the book and the apple B. on the book only C. on neither the book nor the apple D. on the apple only