Final answer:
Hot rolling of iron is performed in the fully austenitic region, which means the process takes place when iron is heated above 912 °C, where it assumes a face-centered cubic structure.
Step-by-step explanation:
The question regarding hot rolling is related to the process of shaping metal by heating it and then rolling it at a high temperature. When we discuss hot rolling in terms of iron, and based on the information that iron below 910 °C has a body-centered cubic structure, hot rolling is actually carried out in the fully austenitic region. This implies that hot rolling is done in the state where iron is in the form of face-centered cubic crystals, which happens when iron is above 912 °C and up to its melting point. Austenite is the high-temperature phase of iron, and rolling in this phase allows the metal to deform easily due to its higher temperature and lower yield strength, making shaping the metal much easier.