Why not cái cờ?
"lá" is the more appropriate/specific classifier.
So 'là' is the classifier. What else does it apply to?
ps. lá, not là
I wrote : Những học sinh đang vẽ cái cờ của nước Nga. But, duo told me that it's wrong, and that I need to put "lá" between vẽ and cờ. Anybody knows why?
"lá" means "leaf" but as a counting word/classifier it's used for "sheet" like objects such as flags.
We serve the Soviet Union