Answer: D. No, because the state owns and operates the metal plant.
Step-by-step explanation:
The State owns and operates the plants and so is allowed to discriminate against non residents.
This principle was established by the United States Supreme Court in Reeves, Inc. v. Stake, 447 U.S. 429 (1980).
In the judgement, the Court held that South Dakota had a right to give it's residents preferential treatment in buying cement from a state owned plant.