You are correct, the answer is C) Copper. According to the Chemical Data Guide for Cargo Inspection, aniline is corrosive to copper. Copper and copper alloys should not be used in contact with aniline, as the aniline will corrode these materials. The other answer choices - nickel, aluminum, and mild steel - are not as susceptible to corrosion from aniline. Nickel and aluminum generally have good resistance to aniline, while mild steel may see some corrosion but not as severe as with copper.