请指出这个关系分句的与其关系词的修饰关系,以及关系词在关系分句中的是什么成分.But in an old man who has known the human joys and sorrows, and has achieved whatever work it was in him to do, the death of fear is som

请指出这个关系分句的与其关系词的修饰关系,以及关系词在关系分句中的是什么成分.But in an old man who has known the human joys and sorrows, and has achieved whatever work it was in him to do, the death of fear is som
请指出这个关系分句的与其关系词的修饰关系,以及关系词在关系分句中的是什么成分.
But in an old man who has known the human joys and sorrows, and has achieved whatever work it was in him to do, the death of fear is somewhat abject and ignoble.
这是新概念英语第四册第十一课中的一句话.这句话应该是说：对于饱经人间甘苦,该作的都已经做了的老年人来说,再要怕死的话就有点可怜和不光彩了.
请问：其中的关系分句it was in him to do 中的it 指的什么,关系分句所修饰的whatever work 在关系分句中哪个词的宾语,或是其它什么成分?
再请问这句话能否这样说： But in an old man who has known human joys and sorrows, and has achieved whatever work for him to do, the fear of death is somewhat abject and ignoble.
或者可否说： but in an old man sho has know human joys and sorrows, and has achieved whatever work that was in him to do, the fear of death is somewhat abject and ignoble.

请指出这个关系分句的与其关系词的修饰关系,以及关系词在关系分句中的是什么成分.But in an old man who has known the human joys and sorrows, and has achieved whatever work it was in him to do, the death of fear is som
Let's start with this: 'It was in him to do important work'. That means, "He was capable of doing important work." In the grammar the subject is 'it', but in the meaning the real subject is "to do important work". You could also say, "To do important work was in him."
Now, we don't know if it's important work. We want to talk about whatever work is in him -- great or small, important or otherwise. So we substitute 'whatever' for the adjective and move that and 'work' up to the front:
(1) It was in him to do important work.
(2) whatever work it was in him to do
(1) is a full sentence, but (2) is a noun phrase: it can be subject or object of a sentence; it means a kind of work. In Russell's sentence it's object of 'achieved' in:
[an old man who] has achieved whatever work it was in him to do
下面是汉语解释：
1）it was in him to do 中的it是形式主语,真正的主语是to do (whatever work).说to do whatever work was in him,就等于说it was in him to do whatever work.现在把whatever work提前,就变成whatever work it was in him to do.
2）that it was in him to do是whatever work的关系分句.关系代词that代替先行成分whatever work,在从句中作do的宾语,所以可以省略.
3）whatever work作has achieved的宾语.

it应是whatever work分句的形式主语，而whatever work在who的分句中是has achieved的宾语。
it作的形式主语没有什么意思，whatever work it was in him to do和 whatever he was to do没什么区别。