Final answer:
The typical duration of a probationary license in many U.S. states is one year, after which a driver may be eligible to upgrade to a full, unrestricted license, but this can vary by location.
Step-by-step explanation:
The length of time a probationary license lasts can vary depending on the state or country where it is issued. Generally, in many U.S. states, a probationary license, which is often issued to new drivers, lasts for a specific duration.
For the purpose of the question provided, if we are considering the typical durations encountered in the U.S., the most common length of time is option (a) One year. After this period, assuming the driver has maintained a good driving record, they may be eligible to upgrade to a full, unrestricted driver's license.
However, since the duration of a probationary license may differ based on local laws, it is important to check the specific regulations of the licensing authority in your area for the most accurate information.