You are troubleshooting a desktop computer that frequently reboots and shorts out. When you open the case, you see that all of the internal components are covered with grime. What should you use to clean the metal contacts on the expansion cards and memory after removing them?

The grime won't likely be removed by compressed air. Computer equipment's electronic connectors should never come in contact with water. Instead, clean contacts by wiping them with a lint-free swab moistened with distilled, denatured isopropyl alcohol (also called electronics or contact cleaner and found in electronics stores). You may have heard advice to use an eraser, but doing so risks damaging the component because it removes a part of the soft gold from the contacts.