Final answer:
In this informal assessment situation, Gabe is concerned with construct validity option (c) when using the Socratic method to check his students' understanding.
Step-by-step explanation:
In this informal assessment situation, Gabe is concerned with construct validity option (c) when using the Socratic method with his students to check their understanding. Construct validity refers to the degree to which a given variable actually captures or measures what it is intended to measure. Gabe wants to ensure that his method is effectively measuring his students' comprehension of the volleyball test.
By using the Socratic method, Gabe aims to probe his students' knowledge, critical thinking, and understanding of volleyball-related concepts, contributing to the construct validity of the assessment.