Some subjects are understood; others are attached to the verb.
● In عَبَدَ, the subject هُوَ is understood but not written.
● In خَرَجَا, dual ا is an attached nominative subject pronoun corresponding to هُمَا.
● In سَجَدُوا, واو الجماعة is attached and corresponds to هُمْ.
● In ذَهَبْنَ, نون النسوة is attached and corresponds to هُنَّ.
Method: read the full form, inspect its ending, then state the corresponding separate pronoun.