Thanks a lot for explaining in such detail. However, if we replace both questions in the given examples, would the meaning change or not?
***** NOT A TEACHER *****
Good morning, tasneemspring.
(1) Thank you for your excellent question.
(2) As another poster pointed out in his excellent post, the meaning of these phrases can change, depending on how you pronounce them.
(a) If you study that poster's comment carefully, I think it will be of enormous help. (It certainly was for me.)
(3) Personally, if I had been on that bus, I would have said to my friend: How about THAT!!! = Isn't THAT outrageous!
(4) Could I have used "What about that" in the bus example? Well, maybe like this:
I: Look at that, will you! No one is standing for the lady.
MY INSENSITIVE FRIEND: What ABOUT that?
(a) In other words, my friend is like those young people who are not standing up for the lady. My friend doesn't see anything wrong. So he says (with complete sincerity): What are you talking ABOUT? Everything looks fine to me!!!
Have a nice day!