He is in doubt as to what is needed.他拿不定主意到底需要什么。
The outcome was still in doubt.结果有待揭晓。
He is in no doubt as to what is needed.他非常清楚需要什么。
英汉双解词典包含368430条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。