doubted

答案B本句的结构是：owe sb. sth. for doing sth. 或owe sth. to do. for doing sth.。

作为副词,undoubtedly和doubtless意义基本相同,undoubtedly强调的意味更大一点.doubtless可以作为形容词.无doubtlessly这一词.

有区别。undoubtedly指的是无疑;毋庸置疑地，的确地;显然;必定。doubtless指的是无疑地;确定地;多半。例句辨析：undoubtedly1、Mr Brooke is undoubtedly in a spot of bother. 布鲁克先生肯定遇到了点小麻烦。2、Mozart"s compositions are undoubtedly amongst the world"s greatest. 莫扎特的作品无疑位居世界上最伟大的作品之列。3、Burke"s sentiments undoubtedly struck a responsive chord in Parliament. 伯克的观点无疑引起了议会的积极回应。doubtless1、He will doubtless try and persuade his colleagues to change their minds.他很可能会试图说服同事们改变主意。2、Doubtless he was justified in some of his criticism of the media. 他对媒体的一些批评性言论无疑是合乎情理的。3、She took off her shoes, doubtless because her feet hurt. 她脱掉了鞋子，大概是因为脚疼。

Undoubtedly是一个副词，而no doubt是一个短语，可以作表语，像that is no doubt

How did he respond when people doubted ( that ) it was true.如果用whether 也是可以的：How did he respond when people doubted whether it was true or not.

你给出的翻译是正确的。英语句子翻译时，要遵从汉语表达习惯，把原因状语because you doubted提前。如果您认可我的答案，请点击下面的“选为满意回答”按钮，谢谢！

大海永远不会怀疑天空的蓝

前者说可能是…，后者指的是可能不是，如果是肯定句doubt后面用whether而不是that。

大体上所表达的意思一致 硬要说区别的话看单个单词的意思吧

你好翻译为：怀疑、疑惑希望可以帮到你

可以，前者是被怀疑的，强调被动，后者是可疑的意思，值得怀疑