Step 1: Clarify the aims of the two early steps.
Problem definition clarifies the decision problem, symptoms vs. causes, and constraints. Approach development frames the research questions/hypotheses, constructs, and analytical model; it also guides which research design will follow.
Step 2: Map typical activities used in these steps.
Secondary data analysis (company reports, syndicated data, academic articles) to understand context, trends, and past findings.
Expert/Key-informant interviews (managers, channel partners, industry analysts) to surface tacit knowledge, refine constructs, and spot feasible variables.
Qualitative research (focus groups, in-depth interviews, ethnography) to explore consumer language, beliefs, and to generate hypotheses/measurement items.
Step 3: Evaluate options.
(a) is used in both steps (background and framing) ⇒ correct.
(b) is a standard exploratory technique at this stage ⇒ correct.
(c) qualitative exploration precedes formal design ⇒ correct.
Therefore the inclusive choice is (d) all of these.
\[
\boxed{(d)}
\]