Text 1 A quantitative researcher argues that a conclusion is more credible when it remains similar under several reasonable ways of defining or measuring the key outcome. If a result appears only under one narrow definition, it may be fragile. Text 2 A study of language learning finds an advantage for conversation practice when progress is scored by vocabulary growth, listening accuracy, and an independent speaking rubric. The size varies, but the direction is the same. Rather than merely noting their shared topic, which choice gives the most accurate principle-and-application account?