Which numbers are designated as non-functioning area codes in clearance practice?

• A. 555-0100 through 555-0199 in all area codes except 800
• B. 555-0123
• C. 800-000-0000
• D. 212-555-0100

Answer: (A)

In clearance practice, numbers that won’t connect to real people are designated to avoid disturbing or misdirecting actual subscribers. The 555 family is reserved for fictional use in media, and a specific block within that family—555-0100 through 555-0199—is set aside as non-functioning in every area code except 800. This blanket rule ensures that most shown numbers won’t route to real lines, which is why the full range is the correct designation. A single number within that block (like 555-0123) is still part of the non-functioning group, but the policy is defined by the entire range, not just an isolated example. Numbers with a different area code outside this block (such as 800-000-0000) aren’t covered by this non-functioning designation, and a number like 212-555-0100 would fall under the same non-functioning block in practice, but the best answer is the complete range across area codes (except 800) rather than a single instance.