- Colons, dashes, question marks, and exclamation marks are ...
- Colons, dashes, question marks and exclamation marks are ...
- Colons, dashes, question and exclamation marks are ...
- Colons, dashes, question, and exclamation marks are ...
The Oxford comma is usually optional, but personally I prefer to use it whenever possible. However, I'm not sure it will be correct to use it in the 4th example. Is it correct or not?