A: Why did you stand there without a word?
B: I didn't know what on earth to answer.
A: Then, why did you say sorry to the teacher?
B: I don't know, I just felt afraid at that time.
A: You should change it.
e.g. “What on earth are you so grave about?” she suddenly demanded.
e.g. How on earth did you manage to get the car started?
e.g. Why on earth did they bother to get married?
e.g. How on earth could I have made so grave a mistake?
1. without a word：一声不吭地，一言不发地
e.g. He walked straight by without a word or without even raising his hat.
e.g. Tom swept up the broken glass without a word of reproof to his son.
e.g. He intruded himself into the conversation without a word of apology.
e.g. He hurried by without a word.
2. say sorry to：向……道歉
e.g. You'll say sorry to me for your impertinence, or you'll quit the office instantly!
e.g. I really ought to say sorry to you for having stood in your light so long.
He had the grace to say sorry to me for the insulting remark.