Juan martinez, a researcher for abc research group, is working on crafting a survey for a client. he is concentrating on framing the questions, selecting response choices, refining the wording, and determining how many questions to ask. in the context of establishing the research design, juan is focusing on the

Juan is focusing on the construct validity of his research design. 

Construct validity refers to the ability of a research design (test or tool) to accurately measure the constructs it aims to measure. In Juan's case, by spending time concentrating on framing the questions, selecting response choices, refining the wording, and determining how many questions to ask, he is ensuring that his survey questions are accurately designed and comprehensively measure the constructs he indents to measure in his survey. 

It’s the answer D and it has been proven