Concept:Computer maintenance involves using safe cleaning methods that do not damage sensitive electronic components.Explanation:Washing dusty parts with soap and water can cause short circuits and corrosion.Keeping the computer exposed to sunlight may lead to overheating and permanent damage.Cleaning the display unit with methylated spirit can strip protective coatings from the screen.Blowing the system unit with a blower safely removes dust from internal parts without direct contact.Regular dust removal using a blower is an effective and recommended maintenance practice.Answer:D. blowing the system unit with blower