ANS:A - heat capacity

At absolute zero temperature (0 Kelvin or -273.15 degrees Celsius), substances typically exhibit a state of minimum energy where their atoms or molecules are in their lowest possible energy states. At this temperature:

1. Heat capacity: At absolute zero, the heat capacity of substances generally tends to approach zero. Heat capacity measures the amount of heat required to change the temperature of a substance by a given amount, but at absolute zero, substances have minimal thermal energy, so there is minimal capacity to absorb or release heat.
2. Crystalline structure: At absolute zero, substances may or may not have a crystalline structure depending on their atomic or molecular arrangement. Absolute zero does not dictate a specific crystalline structure for all substances.
3. Entropy: At absolute zero, the entropy of a perfect crystalline substance is typically zero because there is only one possible microstate for the system. However, real substances may have residual entropy due to imperfections, defects, or quantum mechanical effects.