Final answer:
To properly punctuate and rewrite the sentence, include a hyphen between 'ten' and 'year' and set the year '09' in single quotes to denote a specific year.
Step-by-step explanation:
The sentence 'The graduating class of 09 held its ten year reunion at a Boston Red Sox game in Fenway Park' can be rewritten and punctuated as:
'The graduating class of '09 held its ten-year reunion at a Boston Red Sox game in Fenway Park.'
In this updated version, I added a hyphen between 'ten' and 'year' to correctly indicate that these two words work together as a compound adjective to describe the reunion. Additionally, I enclosed the year '09' in single quotes to indicate that it represents a specific year.
Learn more about Punctuation in written sentences