Three days ago, ()she went shopping alone, she was caught in a shower and fell ill.A. thatB. whichC. whereD. when

本题考查定语从句中关系副词的用法。解题的关键在于判断先行词在从句中所充当的成分，以此来确定合适的关系词。

• 首先明确句子结构，“Three days ago”是时间状语，“she went shopping alone, she was caught in a shower and fell ill”是一个主从复合句，其中“she went shopping alone”和“she was caught in a shower and fell ill”是并列的句子结构，而“()she went shopping alone”是一个定语从句，用来修饰先行词“Three days ago”。
• 接着分析先行词“Three days ago”在定语从句中作时间状语，表示“在三天前她独自去购物的时候”。
• 然后看各个选项：
  • A选项“that”不能引导非限定性定语从句，所以A选项错误。
  • B选项“which”在定语从句中通常作主语、宾语等，不能作时间状语，所以B选项错误。
  • C选项“where”在定语从句中作地点状语，不符合本题先行词在从句中作时间状语的要求，所以C选项错误。
  • D选项“when”是关系副词，在定语从句中作时间状语，符合本题要求，所以D选项正确。