The correct answer is B) blade from overheating. When cutting metal with a power hacksaw, a coolant is used to prevent the blade from overheating. The friction generated during the cutting process can cause the blade to become extremely hot, which can lead to accelerated wear, dulling, and even damage to the blade. By applying a coolant, the heat is dissipated, allowing the blade to maintain its cutting edge and preventing premature failure. The other options are incorrect because they do not directly address the primary purpose of using a coolant in a power hacksaw. Option A) refers to the heat of friction in general, but does not specifically mention the blade. Option C) is about preventing the cut from clogging, which is a separate issue not directly related to the use of a coolant. Option D) is about preventing the blade from bending, which is not the main reason for using a coolant.