Which of the following would increase the rate of rusting of an iron article?

Rusting is an electrochemical process needing water, oxygen and conduction of ions. Dissolved electrolytes such as $\mathrm{NaCl}$ raise the conductivity of the water film and speed up the cell, so (A) increases rusting. Contact with a less active metal (Cu) makes iron the anode of a galvanic couple, so (C) increases rusting. Without oxygen the cathodic reaction cannot occur, so (B) does not increase rusting, and zinc coating protects iron sacrificially, so (D) decreases it.