C. plastic toy
D. both petroleum and paper
This question was addressed to me in an interview for job.
Origin of the question is Corrosion and its Classification in section Corrosion Principles of Corrosion Engineering
Explanation: The operating conditions in both the petroleum and paper industry are mainly in aqueous state with various chemicals in it. Hence these are likely prone to various electrochemical reactions which causes corrosion. Maintenance works include periodic inspection and replacements of partially corroded parts. It minimizes costly catastrophic failures, unscheduled down time, resulting in increased production and revenue.