I typed 'I don't have any hair'. It is unlikely I would say I have no hair when expressing myself normally, because in English we refer to hair being a collective therefore it is a negative of a collection rather than of one. However I was marked wrong. Why?
I've added it. It was a new sentence lacking alternatives - that happens sometimes! I can only echo the advice to send reports for answers that should be accepted. They find their way into the system eventually, if they are correct.