单选题 Nerve signals may travel through nerve or muscle fibers at speeds as high as two hundred miles per hour.
  • A. velocities
  • B. impulses
  • C. ratios
  • D. percentage


【正确答案】 A
【答案解析】speed和velocity同义,意为“速度”;impulse:冲动、刺激、推动;ratio:比、比率;percentage:百分数、百分率。