A 
is used to show a large pause or interruption in thought within a sentence.
A comma does not make sense because all a comma does is separate elements in a sentence; a colon separates thoughts and/or enumerations.
Thus, dash was the only reasonable answer.
You're welcome.
A comma does not make sense because all a comma does is separate elements in a sentence; a colon separates thoughts and/or enumerations.
Thus, dash was the only reasonable answer.
You're welcome.