Answer is A.
Bearings reduce friction by providing smooth metal balls or rollers, and a smooth inner and outer metal surface for the balls to roll against. These balls or rollers 'bear' the load, allowing the device to spin smoothly.
The concept behind a bearing is very simple. Things roll better than they slide. The wheels on our car are like big bearings. If we had something like skis instead of wheels, our car would be a lot more difficult to push down the road.
That is because when things slide, the friction between them causes a force that tends to slow them down. But if the two surfaces can roll over each other, the friction is greatly reduced.