On a slow-speed diesel engine vessel equipped with an ALCAP fuel oil purification system, what would be a symptom of an opening solenoid valve leaking by?

Correct Answer: Option B — An increase in the rate at which the purifier sludge tank is rising.

An opening or closing water solenoid valve leaking by continuously admits sealing water into the purifier bowl, causing water to escape into the sludge space. This continuous leakage drastically increases the rate at which the purifier sludge tank fills and rises.