I had to choose from words much, many, too much, too many. Why isn't my answer correct? What was the right variant and why?
For me it is a matter of style whether to write many or too many here. Neither alternative with much is right at all. In fact I would have said I am too busy today, I have so many things to do but your test does not even recognise that version. I suppose they do not like the repetition of too but that does not make the sentence wrong.