这道题答案选C,正确，在你的这道题中，though failed = though it was failed, failed为过去动词（被动语态），如：He failed the exam. though failed的用法多见于书面语。

请看原文书籍中相关句子：

1.Horror film purists may object to the levity even though failed, as a lot of it is.

2. Tucker persuasively argues that Pickett's Charge, though failed in its execution, actually reveals Lee at his most masterful.

3. Various individuals in the pre-1970 Palestine who promised, though failed, to perform miraculous signs similar to those in the biblical tradition about the exodus and conquest.

1.不成立. 字典里讲了failed作形容词只能放在名词前。

2.此句有连词though，所以可以有两个谓语。也就是failed是fail的过去式。省略了主语he

Though (he was省略了 )failed, the man would not give in.

A. Though had been failed   B. Though having been failed   

C. Though failed       D. Though being failed

解答：以上是“保留连词的过去分词” 作让步状语。分词作状语，其逻辑主语就是后面句子的主语。

Though failed, the man would not give in.

=Though he was failed , the man would not give in.

参考译文：虽然这个男人失败了，但是他不会认输/屈服。

【1】 fail   vt. 不及格 (英文解释：If someone fails a test, examination, or course, they perform badly in it and do not reach the standard that is required.）

I lived in fear of failing my end-of-term exams.  我总是担心期末考试不及格。

【2】fail   vt.评定…不及格;使不及格(英文解释：If someone fails you in a test, examination, or course, they judge that you have not reached a high enough standard in it.）

They were the two men who had failed him during his first year of law school.  

他们是在法学院一年级时让他不及格的两个人。