单选题 Racing the clock every day is such an exhausting effort that when I actually have a few free moments, I tend to {{U}}collapse{{/U}}.
  • A. fall down
  • B. fall in
  • C. fall out
  • D. fall behind
【正确答案】 A
【答案解析】[解析] collapse“塌陷”，四个选项：fall down“掉下，倒下”；fall in“病倒”；fall out“吵闹，争吵”；fall behind“落后”；所以A项符合题意。