Explanation
Choice B is the best answer. The word "ambivalent" means contradictory. The text states that the mechanism behind oxygen in winemaking could either prevent or accelerate wine spoilage. This means that the role of oxygen in fermentation can have either one of two opposite impacts.
Choice A: "favorable" means beneficial. That oxygen could either prevent or accelerate wine spoilage makes its role not strictly beneficial in winemaking.
Choice C: "tainted" means stained with disgrace. It would not make sense that the ability to either prevent or accelerate wine spoilage would be shameful.
Choice D: "swift" means prompt. The text does not mention the rate at which oxygen influences microbial activity in wine.
✨ Expert's Tip ✨
Identify the key phrase in the text ("...either prevent or accelerate…") that hints at the nature of the oxygen's role.