答案：C

题目分析：从句式来看Travelling west及 travelling east, you set it ahead.可知两者相反，ahead向前，back向后，behind在…的后面，forward向前的；结合句意：到西方旅行，你应该将你的钟往回调；到东方旅行，你要将你的钟向前调。故选C.

点评：方位副词常考的还有where,there, up, down, away, nearby, home, ahead, abroad, indoors, overseas, halfway, upstairs, downstairs 等，平时的学习及备考中遇到了相应的题目要进行总结，并牢记与动词组成的固定短语，考试才能有备无患。