The correct answer is C) clean dry cloth. Grease accumulations on electrical contact surfaces should be removed using a clean, dry cloth. This helps to avoid increasing the contact resistance, which can lead to issues with the electrical system. Using a dry cloth is the preferred method, as it effectively removes the grease without introducing additional moisture or contaminants that could further degrade the electrical contacts. The other options are not recommended: A) a 10% solution of carbon tetrachloride solvent and water could leave residues that could interfere with the electrical contact; B) a small wire brush could potentially damage the contact surfaces; and D) a compressed air jet could push the grease deeper into the contacts or spread it to other areas.