In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".

[header] How to clean a vornado fan [title] Clean out dust in the outer grills using a vacuum cleaner brush. [step] You can use a brush attachment on a vacuum cleaner to clean out all of the dust from the outer grills. Make sure the fan is unplugged before vacuuming. <sep> (A) [title] Place a cleaning rod in each section of the fan and squirt some cleaning fluid through each rod. [step] Avoid getting any grease in the vents or rest tray. (B) Some of the cleaner should be removed from the outside if you use a cloth and brush as cleaning instructions are laid out in the manual. [substeps] Avoid cleaning the outer grills with dust because it can detach some of the insulation and contribute to the fan's cooling. (C) Wipe down the inside of the cover every few minutes so you can put the fan back together. [substeps] For maximum efficiency, you should wash your vornado fan at least once a month, which is right after each dry run. (D) Go slowly when vacuuming to ensure you clean out as much dust as possible. [substeps] This will only clean the outer part of the fan, not the inside blades.
D