How does this answer the son's question?
Ramban (on Pasuk 20): We tell him all about Yetzi'as Mitzrayim, which teaches us that Hashem is the Creator who wants us and who is all-capable - "le'Eineinu" 1 - which we witnessed with our own eyes. 2
Seforno: We explain to him that since we were slaves in Egypt and therefore unable to attain the perfection that is required of us, Hashem performed wonders to take us out from there and to bring us to the land, to enable us to reach that perfection . 3
Moshav Zekenim (in Bo Sh'mos, 12:26): The Chacham sees that we are eating the Chagigah, and then the Pesach when we are all but satiated, and he asks why we don'tt we should eat the Pesach - which is the primary Mitzvah, first. And we answer that it is forbidden to eat anything after the Korban Pesach.
