题目

 I enjoyed the pictures of the river and they brought back the old days _____ I swam in it.    A. when          B. that         C. who              D. where 答案： A。本句中先行词为the old days，后面应使用关系副词when引导定语从句，when在句子中作时间状语。下列装置用于实验室制取CO2，不能随开随用、随关随停的装置是A.B.C.D.