Which of the following has correct punctuation?

1.   ?    Mr and Mrs Smith will join us later for dinner.
2.   ?    She is a scientist who specializes in A.I.D.S. research.
3.   ?    The price of our stock has risen by 25,5%.
4.   ?    My hometown is Chicago, Ill.

Which sentence shows the correct use of an exclamation mark?

1.   ?    Help. I'm falling.
2.   ?    Yuck! It smells terrible in here!
3.   ?    Are you really going to do it!
4.   ?    What a beautiful day.