How does the slicer on the acrylic mirror serve a dual function?

The acrylic mirror's slicer performs a dual function primarily as a tool for both signaling and shaving. This means that the slicer can be used to create visible signals, such as signals to other observers in a tactical operation, while also functioning as an implement for shaving. This dual capability is particularly valuable in various scenarios where both tasks might be necessary.

The option related to cutting and assembling, while plausible in some contexts, does not accurately represent the specific functions associated with the acrylic mirror's slicer, which is specifically designed for signaling and personal grooming. The measuring and scoring option does not align with the intended use of the slicer as a multifunctional signaling tool. Similarly, compressing and expanding speaks to functionalities that are unrelated to the operations typically performed with the slicer, which revolve around visibility and grooming rather than physical manipulation.