relative balance between acid and alkali

例句：

1. 1. The relative humidity is 60%.
   相对湿度为60%。
2. 2. Therelative positions of the two stars are determinedby their distances from each other.
   两颗星星之间的相对位置由它们彼此之间的距离决定。
3. 3. The relative sizes of the two objectscan be compared by measuring their lengths.
   通过测量两个物体的长度，可以比较它们的相对大小。