单选题 He came back later, ______ which time they had left.
  • A. after
  • B. by
  • C. from
  • D. for
【正确答案】 B
【答案解析】[解析] by与时间搭配表示时间的限时。本句相当于“By the time he came back later, they had left”。B选项正确。