Diagrams show Y as input driving demand for X

Steps:

• Identify diagrams depicting production where Y serves as a resource for producing X.
• Observe demand for Y fluctuating based on X's market demand.
• Confirm no direct consumer interaction between X and Y.
• Link this to indirect demand derivation in production chains.

Why C is correct:

• Derived demand occurs when demand for an input (Y) arises from demand for the output (X) it helps produce, per standard microeconomic theory.

Why the others are wrong:

• A: Complements require simultaneous consumer use of X and Y, not evident in production-focused diagrams.
• B: Substitutes involve competitive consumption of X and Y, unrelated to input-output links.
• D: Joint supply implies X and Y co-produced simultaneously, opposite of Y enabling X.

Final answer: C