constant unit price

例句：

1. 1. The temperature is constant throughout the day.
   温度在整个一天中保持不变。
2. 2. The sun always rises and sets at the same time every day.
   太阳每天在同一时间升起和落下。
3. 3. The river flows steadily, making it a constant source of life for the surrounding area.
   这条河流流动稳定，为周围地区提供了持续的生命支持。