Given:

p: The bib is a bub.

q: The bub is a bub.

Which of the following is logically equivalent to /?

If the bib is a bub, then the bub is a bab.
If the bub is not a bab, then the bib is not a bub.
If the bib is not a bub, then the bub is not a bab.
If the bib is a bub, then the bub is not a bab.