कॅलरीची व्याख्या अशी करता येईल की, 1 किलोग्राम पाण्याचे _______ तापमानामध्ये 1° तापमान वाढण्याकरिता लागणारी ऊर्जा.

The correct answer is Option A (15° celsius).

Key Points:
• Standard Physical Definition of a Calorie (The 15° Calorie):
• In thermal physics, the specific heat capacity of water varies slightly at different ambient temperatures.
• The Standard 15°C Calorie Definition:
• To achieve international metrological precision, the standard kilocalorie (or large Calorie) is formally defined as the exact amount of thermal heat energy required to raise the temperature of 1 kilogram of pure water by 1°C from 14.5°C to 15.5°C at standard atmospheric pressure (101.325 kPa).
• This globally recognized benchmark corresponds precisely to the 15° Celsius reference temperature baseline.
• Final Answer Key Match:
• Option 1 (15° celsius) represents the internationally standardized definition confirmed by the official key.
• Key Takeaway: The standard calorie is physically calibrated as the heat required to raise 1 kg of water by 1°C specifically at 15°C (from 14.5°C to 15.5°C).