Which sentence correctly uses an exclamation mark? 

1. Wow! That was amazing
2. Wow! That was amazing!
3. Wow. That was amazing!
4. Wow, that was amazing

Exclamation marks express strong emotion but should be used sparingly in formal writing. One per sentence suffices (option a). Option b is over-emphatic. Periods (option c) or commas (option d) dull the excitement. Reserve for genuine interjections or commands (e.g., “Stop!”).