Final answer:
In Block 2 of the CMS-1500 form, the patient's last name, first name, and middle initial are separated by a comma in the format: 'Last Name, First Name, Middle Initial.'
Step-by-step explanation:
When entering a patient's name in Block 2 of the CMS-1500 claim, the correct way to separate the last name, first name, and middle initial is with a comma. The format should be Last Name, First Name, Middle Initial if known. This formatting is similar to the standards used when citing authors in various documentation styles, where you would also give the last name followed by a comma, then the first name and middle name initial, ending with a period. Therefore, for the CMS-1500 form, you would use option 1) With a comma.