【题目】The book has helped me greatly in my daily communication, especially at work ________ a good impression is a must.
A.which
B.when
C.as
D.where

【答案】D
【解析】句意：这本书对我的日常交际有极大的帮助，尤其在工作中，良好的印象是必须的。句中的先行词为work，在从句a good impression is must中作地点状语，故用关系副词where。故D正确。