Answer:
Exclamation point
Explanation:
An external punctuation mark is used to signal the end of a sentence.
Of the four given options, only an exclamation point signals the end of a sentence.
Dash (—) is an example of internal punctuation.
Hyphen is a short line (-) that connects the parts of a compound word.
Apostrophe is a punctuation mark (') that indicates either possession or the omission of certain elements, and so it cannot be external punctuation.
