The temperature at which one crystalline form changes to another is called _ temperature.

Explanation

Option A: The critical temperature refers to the temperature above which a substance cannot exist as a liquid, regardless of the pressure. This is commonly seen in the context of supercritical fluids.Option B: The absolute temperature is a temperature scale that is based on absolute zero, the theoretical temperature at which all matter would have zero thermal energy. This temperature scale is commonly used in scientific applications.Option C: At the 'Transition temperature' a material changes from one allotropic crystal state to another. To be more specific, at the 'Transition temperature', two crystalline forms of a substance can co-exist in equilibrium.Option D: "None of these options is correct" is also incorrect as the correct answer is (C) Transition.