Question

whatever work it was in him to do这句看不懂

But in an old man who has known human joys and sorrows, and has achieved whatever work it was in him to do，

Answer 1

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。
语法解释：
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。