Most of the fractional horsepower motors have either

The correct answer is: B. ball or roller bearings

Ball and roller bearings are the most common type of bearing used in fractional horsepower motors. They are made of two parts: a raceway and a rolling element. The raceway is a ring that the rolling element rotates on. The rolling element can be a ball or a roller. Balls are round and rollers are cylindrical.

Ball and roller bearings are very efficient and have low friction. They are also very durable and can withstand a lot of wear and tear. These bearings are also very easy to maintain and can be replaced easily.

The other options are incorrect because:

• Hard and annealed bearings are not commonly used in fractional horsepower motors. They are more expensive and not as durable as ball or roller bearings.
• Soft and porous bearings are not commonly used in fractional horsepower motors. They are not as durable as ball or roller bearings and can wear out quickly.
• Plain or sleeve bearings are not commonly used in fractional horsepower motors. They are not as efficient as ball or roller bearings and can generate more heat.