Why does "vandaag" have an extra "a"? Compared to, say, "maandag" or just "dag"?
Vandaag was originally vandage at a time when Dutch still had a case system.
"Wie zijn er de werknemers vandaag?"
Previous lesson said most "Wie" questions require er?
Er is used when the people who refers to are indefinite. However, in this sentence it refers to the employees/de werknemers. Hence er is not used.
Waarom niet dit: "Wie zijn de werknemers van vandaag?"