The correct answer is B) The request would be written as a special instruction in the chief engineer's night order book. This is the correct answer because the chief engineer's night order book is the appropriate place to record special instructions or important information that needs to be communicated to the engineering watch standers. Entering the request in the night order book ensures that the information is clearly documented and passed on to each successive watch, which is crucial when the oily-water separator will be out of service for an extended period. The other options are not the best choices because a note in the coffee mess (A) may be overlooked, and a standing order (C) is more appropriate for long-term, routine procedures. Relying on verbal communication (D) carries the risk of the information not being properly passed on to the next watch.