I am confused about why 'o' and 'un' are left out of this sentence.
They do not require it here, but the article is required in English here.
As a native speaker of a romance language (Portuguese) we just dont need use the articles all the time. Its normal just to say "Eu sunt băiat" not saying the "un".
Ps: Romanian is a romance Language as well !!
Are there other instances where the article isn't required?
I am not very sure, but I think this works mostly with human-related things, such as: man, woman, girl, boy, teacher, worker, engineer etc.
Like in other Romance languages, they kinda work like adjectives meaning that you are a boy/girl/man/woman
I put the right answer...? I have no idea why its saying something else. I checked it 3 diffrent times.