Which of the following is NOT a type of disposal unit?

The choice of multi-purpose as the option that is not a type of disposal unit makes sense within the context of disposal methods used in phlebotomy and similar healthcare settings.

In medical practice, disposal units are designed to ensure the safe and effective disposal of various types of waste, particularly biohazardous materials. Reusable units are intended for items that can be cleaned and sterilized for repeated use, which is common for some medical instruments, but not typically applicable to waste disposal. Single-use units are designed for one-time use and are disposed of immediately after their function is fulfilled; this is standard for many disposable medical items to minimize contamination risk. Sharps containers are specifically designed for the safe disposal of sharp objects like needles and blades to prevent injury and infection.

On the other hand, the term multi-purpose does not refer to a standardized category of waste disposal in medical or phlebotomy contexts. Disposal systems are categorized based on their intended use, and "multi-purpose" does not clearly convey a recognized type of disposal unit for biohazardous waste. Thus, it stands apart in terms of nomenclature and application from the others, making it the correct choice for what is not a type of disposal unit.