Final answer:
The correct placement of the comma in the date 1)June 12, 1999, is between the day and the year, adhering to American English conventions.
Step-by-step explanation:
The comma in the date 1)June 12, 1999 belongs between the day and the year,
hence the correct placement is between 12 and 1999. T
his date format follows the conventional American English style which sequences the date as month, day, then year, with a comma separating the day from the year.
The provided examples, such as the death of Nobel Prize winner Toni Morrison on August 5, 2019, further confirm that this is the standard formatting for dates in written English.