Which of these is a valid DEA Registration number for a mid-level practitioner?

A valid DEA Registration number for a mid-level practitioner is formatted according to specific guidelines established by the Drug Enforcement Administration (DEA). Mid-level practitioners, such as nurse practitioners or physician assistants, typically have registration numbers that start with specific letters and are followed by a unique combination of numbers.

In this case, the correct answer is valid because it starts with the appropriate letter for mid-level practitioners. Specifically, mid-level practitioners have registration numbers that begin with either "M" or "X". The number itself is composed of a series of digits following the initial letter, allowing for individual identification.

The other options do not conform to the expected format for mid-level practitioners. For example, options that utilize letters or numbers that fall outside of these conventions would not be valid. Thus, the answer that fits the criteria for a mid-level practitioner's DEA number is indicative of understanding the specific registration requirements enforceable by the DEA.