单选题 The levels of PM2.5 in Beijing are {{U}}by far{{/U}} the worst since the government began releasing figures on PM2.5 particles.
  • A. by a considerable margin
  • B. until the present moment
  • C. over a large area
  • D. according to most people
【正确答案】 A
【答案解析】by far：毫无疑问地，绝对地，很大程度上；by a considerable margin：差距大。