单选题 Upon returning to the classroom, ______.
  • A. a letter was on the desk
  • B. he found a letter on the desk
  • C. a letter was found on the desk
  • D. the desk had a letter on it
【正确答案】 B
【答案解析】[解析] Upon (On) doing something = as soon as/the moment/the minute/the second/the instant等时间连词，表示：一……就……。