Which word best matches the meaning of "breakneck"?

Explanation

"Breakneck" refers to something occurring at an extremely fast pace, often dangerously so. Here's why the other choices do not fit: A. Unhurried: Implies a slow, relaxed pace, which is the opposite of "breakneck." B. Hazardous: Although "breakneck" can suggest danger, this word does not specifically indicate speed. C. Sluggish: Means slow or lacking speed, directly contradicting "breakneck." D. Fast: Accurately captures the sense of very high speed inherent in "breakneck." E. Swift: While similar to "fast," it was not the designated correct answer. Therefore, "fast" is the most appropriate synonym for "breakneck."