By在表被动的时候能省略吗?

eveliyi

在用＊＊self的时候，by可以省略。

风过疏竹

白勇第九章42题,

Joplin's faith is his opera ' Tremonisha' was unshakable, in1911 he published the score at his own expense and decided on staging it himself.

A on staging it himself

B that he himself would do the staging

C to do the staging of the work by himself

D that he himself would stage it

E to stage the work himself

虽然也明白, to do the staging of the work 没有to stage the work 简洁,好, 但是, 不明白 by himself的by为什么可以省略?

答案为E