Which two punctuation marks are used to offset a parenthetical element in a sentence?

comma

semicolon

dash

hyphen

I would also say comma and semicolon. I learned about this last year. Why is it not the other two?

The hyphen is used for something like this, "short-term" that's an easy way to use an hyphen though.

A dash is somewhat like a hyphen. It's like a longer minus sign you could say.
"It was said by—Thomas Williams." (Random person I made up.)

Semicolon and comma would be the best answers, I believe. They bring together sentences.