The Federal Motor Carrier Vehicle Safety Standard number relevant to tire specifications is:

The correct choice identifies the Federal Motor Carrier Vehicle Safety Standard related specifically to tire specifications. The regulation under 49 CFR Part 571.139 covers the federal standards that set forth the minimum safety requirements for motor vehicle tires. These standards ensure that tires meet certain performance criteria to promote safety and reliability for vehicles in operation on public roadways.

Understanding the importance of these regulations is crucial for anyone involved in the automotive industry, particularly in tire servicing. These standards cover various aspects such as tire construction, performance testing, labeling, and maintenance requirements, all of which are essential for ensuring the safety of drivers and passengers.

The other options do not reference the proper regulatory framework pertaining to tire specifications, as they cite incorrect sections or numbers that pertain to different areas of vehicle safety or regulations. Thus, the correct answer effectively highlights the specific regulation that addresses tire safety standards, which is vital knowledge for professionals in the automotive field.