Answer: B

Reasoning: The original canine-retraction spring described by Gjessing was formed from a 0.016 × 0.022-inch rectangular stainless-steel wire, as detailed in his biomechanical design paper and confirmed by later clinical studies of the “Gjessing retraction arch” [Gjessing, 1985, PMID 3857860; Dinçer & Işcan, 1994, PMID 7957657].