According to the guidelines of good journalism, which of the following sentences is correct:

A. 9-year-old John Messer broke his wrist when he fell off a skateboard***
B. John Messer, 9, broke his wrist when he fell off a skateboard.
C. John Messer, nine, broke his wrist when he fell off a skateboard.
D. John Messer, a nine-year-old, broke his wrist when he fell off a skateboard.

Option B is correct. According to the guidelines of good journalism, it is recommended to include the name of the person the story is about, along with relevant information, such as their age or occupation. Putting the age after the name, separated by a comma, is the preferred way to do it. This makes the sentence easier to read and avoids any ambiguity. Therefore, "John Messer, 9, broke his wrist when he fell off a skateboard" is the correct sentence.