Final answer:
The correct labeling for a package with an exposure rate of 50 mrem/hr depends on regulatory guidelines, which outline the levels of radiation that correspond to Yellow II or Yellow III labels.
Step-by-step explanation:
The exposure rate at the surface of a package is measured to determine the appropriate label that must be adhered to the package when it is shipped, according to regulations for radioactive materials. In this case, the exposure is 50 mrem/hr (millirem per hour). The labels for radioactive packages are determined by specific ranges of radioactivity and potential exposure levels. These labels include White I, Yellow II, and Yellow III, which signify increasing levels of radiation. The correct label in this scenario is dependent on regulatory guidelines that specify the limits for each label category. However, typically a Yellow II or Yellow III label may be required, depending on the specific regulations in place.