Final answer:
The calorie is defined based on the specific heat capacity of water (H₂O). Water has a very high specific heat, making it very resistant to changes in temperature.
Step-by-step explanation:
The calorie is defined based on the specific heat capacity of water (H₂O). The specific heat of a substance is the amount of energy required to raise the temperature of 1 gram of the substance by 1°C.
In the case of water, it has a very high specific heat compared to most other substances, which means it can absorb a lot of heat before it starts to get hot. To answer the student's question directly, the calorie is based on the specific heat capacity of substance A) H₂O.