The correct answer is C) They are usually pressed on to their shafts. Antifriction bearings, such as ball bearings or roller bearings, are commonly used in pump applications. These bearings are typically pressed onto the shaft to ensure a tight fit and proper alignment. This is necessary to prevent any movement or play between the bearing and the shaft, which could lead to premature bearing failure. The other answer choices are incorrect: A) The outer race should be free to turn in its housing, not the other way around. B) Proper alignment is, in fact, a critical factor in the installation of antifriction bearings to ensure optimal performance and bearing life. D) The inner race, not the outer race, should be tightly fitted to the shaft.