Final answer:
A cold-solvent tank, not water, air, or acid, is used for degreasing metal parts, as solvents effectively dissolve oils and greases at room temperature. The correct answer is (B) Solvent.
Step-by-step explanation:
A cold solvent tank is typically used to clean grease and oil off of parts. Solvents are liquid substances capable of dissolving or dispersing grease, oil, and other contaminants from surfaces. In industrial and automotive settings, a cold solvent tank is a common cleaning method employed to remove stubborn residues from various components. The term "cold" indicates that the solvent is used at room temperature or without the need for heating.
Water (Option A) is not commonly used for cleaning grease and oil because these substances are not easily soluble in water. Instead, solvents are preferred for their ability to break down and lift oil-based substances effectively. Air (Option C) is not a cleaning agent but may be used in conjunction with other methods for drying cleaned parts or surfaces. Acid (Option D) is generally not used as a cleaning agent for grease and oil removal due to its corrosive nature, which could damage the parts being cleaned. Therefore, the correct answer is (B) Solvent.