在英语语法中，当原因状语从句的主语与主句主语相同，或者主语为不定式短语或动名词短语时，可以省略原因状语从句的主语。然而，这种用法只适用于口语和非正式写作中，正式的写作和文学作品中应避免使用。
当主语与主句主语相同时
例如：As I was feeling tired, I decided to go to bed early. 可以省略原因状语从句的主语，变为：Feeling tired, I decided to go to bed early.
当主语为不定式短语时
例如：I went to the store to buy some milk because I ran out of it. 可以省略原因状语从句的主语，变为：I went to the store to buy some milk, running out of it.
当主语为动名词短语时
例如：I missed my flight because I was stuck in traffic. 可以省略原因状语从句的主语，变为：I missed my flight, being stuck in traffic.
需要注意的是，省略主语的原因状语从句只适用于口语和非正式写作中，正式的写作和文学作品中应该避免使用。
