他在比赛中获得了一等奖，迈出了他成为职业小提琴家的关键一步。(mark)

He won first prize in the competition, which marked a critical step in his journey to becoming a professional violinist.

考查句子结构和时态。“他在比赛中获得了一等奖” 在句中充当主句，主语 “他” 译为he，“在比赛中” 译为in the competition，“获得一等奖” 译为win first prize；后半句 “迈出了他成为职业小提琴家的关键一步” 可用which引导的非限制性定语从句表达，先行词为前面的主句，“迈出关键一步” 译为mark a critical step，“成为职业小提琴家” 译为becom a professional violinist，in his journey to ... (在……的旅途上) 强调过程，to为介词，后跟动词的动名词形式。本句陈述的是过去发生的事情，应用一般过去时。故翻译为：“He won first prize in the competition, which marked a critical step in his journey to becoming a professional violinist.”。