plain ball bearing

例句：

1. 1. The plain clothes made her look more professional.
   朴素的衣服让她看起来更专业。
2. 2. He wore a plain shirt to the party.
   他穿着一件朴素的衬衫去参加派对。
3. 3. She prefers plain food over fancy meals.
   她更喜欢朴素的食物而不是华丽的餐点。