The correct answer is D) Delicate parts should be cleaned with a brush and an approved safety solvent. This is the correct answer because the proper way to clean electrical contacts is to use a soft brush and an approved safety solvent, which will not damage the delicate parts. Magnetic brushes can cause metallic dust to adhere to the contacts, compressed air can blow the dust into other areas, and greasing the contacts will increase the contact resistance, which is undesirable. The Coast Guard regulations emphasize the importance of using the appropriate tools and materials to maintain the integrity of electrical systems, and cleaning with a brush and approved solvent is the recommended method for cleaning delicate electrical contacts.