Hi Tuyet Tinh Han, I too have been looking and I can't find a table dedicated to the saving of answers of quizzes. There is, however, a report on Response History so it is, I suspect, a flat file stored in the Moodledata directory, rather than a table or set of tables in the db. It is also likely that this is just the answer, right or wrong, and further data is drawn from the quiz itself.
I suspect too that in the event of such a table, it is likely to grow somewhat drastically, think about it, saving the full quiz taken by every student? That would be an awful lot of data in a very short space of time. Having said all this, however, I can't guarantee that my logic is correct here, only that I too can't find a table that would suit your requirement.
