什么是滚珠丝杠松动？

1. Up the stairs slowly crept the old man, his hands gripping the banister tightly. 2. Into the room burst the excited children, their laughter filling the air. 3. Through the dark forest wandered the lost hiker, his flashlight flickering weakly. 4. Down the street raced the speeding car, its tires screeching on the pavement. 5. Across the stage strode the confident actor, his lines memorized perfectly. 6. Over the fence leapt the agile cat, its fur bristling in excitement. 7. Up into the sky soared the majestic eagle, its wingspan expansive and beautiful. 8. Through the crowded market weaved the determined shopper, her eyes scanning for the perfect bargain. 9. Around the bend came the roaring train, its whistle blaring loudly. 10. In the distance loomed the ominous storm clouds, their darkness foreboding.