Final answer:
Unstained smears being sent to a reference laboratory should generally be 4) stored at room temperature, unless otherwise instructed by the lab or if a freeze-thaw cycle is needed for the specimen's preservation.
Step-by-step explanation:
When preparing unstained smears for transport to a reference laboratory, it is important to maintain the post-preparative stability of the specimen. For long-term storage or when samples need to be sent over long distances, the specimens are often frozen. Freezing at ultra-low temperatures such as -70°C or lower stops the degradation of the tissues and preserves their structure for later examination under the microscope. However, for unstained smears that are being sent for analysis, it is not always practical or necessary to freeze them, and they do not require the same level of temperature control as live cultures or medical specimens. In the absence of explicit instruction from the reference laboratory or evidence of the need for a freeze-thaw cycle, the smears can be stored at room temperature, ensuring they are properly packaged to prevent damage during transport.