Why does the Torah see fit to mention "Oh Ben Yigach Oh Bas Yigach"? Why might we have thought otherwise?
Ramban #2: Because when an ox kills a grown-up, it is wicked (like a wild bear). Consequently, if the owner has been warned three times and allows it to happen a fourth time, he deserves the death-penalty with an option of paying Kofer. Not so children, who tend not to be afraid of them 3 and for the ox to kill a child is more of a natural occurrence; we might have therefore thought that the owner is Patur.
Why does the Torah begin the Pasuk with the word "Oh"?
Ramban #1: It means literally "[if it (the ox) gores a man, or a woman,] or a son (a Katan) or a daughter (a Ketanah) ... ".
Rashi writes that our verse obligate even if it killed a minor. Why do we need a verse to obligate for killing an adult?
Riva citing R"A: We might have thought that he is liable only for minors, for they do not know to guard themselves, but not for adults. Do not answer that verse 29 is needed to include biting, pushing and kicking. This does not explain why it says "Ish Oh Ishah"!