When a big earthquake strikes, it does not do equal harm everywhere. Places resting on ＿＿（1）＿＿ sediment will shift around a lot and are thus likely to be damaged badly. ＿＿（2）＿＿ resting on bedrock are normally better off – though not if they are stuck at the end of a rocky promontory that ＿＿（3）＿＿ a quake's vibrations in the manner of a tuning fork. Finding the areas most badly damaged, and ＿＿（4）＿＿ most urgently in need of assistance, in an area whose ＿＿（5）＿＿ is not already well understood is thus a high-stakes game of hide-and-seek.
therein 意為「在其中（in that place/area）」，短文空格4填入後為「those most urgently in need of assistance therein」，指「在該地區中最緊急需要援助的地方」，與短文「in an area whose [geology] is not already well understood」前後呼應，語意完整且自然。
therefore 意為「因此」，為因果副詞，但空格位於 finding 與 most urgently in need 之間，屬並列補充關係而非因果，與短文句構不符，故錯誤。
D✓ 正確
therein 意為「在其中（in that place/area）」，短文空格4填入後為「those most urgently in need of assistance therein」，指「在該地區中最緊急需要援助的地方」，與短文「in an area whose [geology] is not already well understood」前後呼應，語意完整且自然。
