[往届老友]偶的英语错题，求解~~~！

16. It was not until she had arrived home _____ her appointment with the doctor.
       A. did she remember          B. that she remembered
       C. when she remembered      D. had she remembered
      为什么选B不选D？
17. It was in Beihai Park___they made a date for the first time______the old couple told us their love story.
      A. where, that  B. that, that  C. where, when  D. that, when
    为什么选A不选C？
20. Was___Bill,____played basketball very well, _____  helped the blind man across the street.
     A. that, that, who    B. it, that, that   C. it, who, that      D. this, who, who
        为什么选C不选D？
21. --- Were you early enough to catch the metro last night?
   ---Much too late! It was already midnight ____ I got to the station______ none was going.
A. when, as  B. that, before  C. since, until  D. before, when
        为什么选D不选A？

16,17,20都为强调句的考试重点．
１６：用that引导
１７：强调句前边的空为插入语，第二空为强调内容用that引导，第一空缺把前面的名词带回去须加介词in Beihai Park＝where
２０：考翻译，太晚了，在我到达之前车已经开走了
本人愚见

侠夏侬HO ~~~~~~~~~~~~~~~~~~~~~~~~！！！！！！！！！！！！
 

                  

it is before中before译为才