touch-stone

例句：

1. 1.The touch-stone of our relationship is trust.
   我们关系的基础是信任。
2. 2. The touch-stone of the experiment was the accuracy of the results.
   实验的试金石是结果的准确性。
3. 3. The touch-stone of their success was hard work and dedication.
   他们成功的关键因素是努力工作和奉献精神。