Final answer:
For YES or NO entries in a CMS-1500 claim, an X should be entered. This practice is standard for medical claim forms and ensures accurate processing.
Step-by-step explanation:
When filling out the CMS-1500 claim form, if a response requires a YES or NO entry, you should enter Option 2) An X. This is the standard practice for completing medical claim forms that are processed by health insurances and other healthcare payers. Marking an X in the appropriate box indicates a definitive answer, which is crucial for the proper handling of the claim and to ensure accurate processing of the patient's medical claim.