Final answer:
The two commonly used units to measure heat are the calorie and the joule, with joule being the SI unit of energy and calorie being the energy needed to raise the temperature of 1 gram of water by 1°C. So the correct option is A.
Step-by-step explanation:
The two units of measurement commonly used to measure heat are calorie and joule. The joule (J) is the SI unit of energy, and one calorie (cal) is defined as the energy required to raise the temperature of 1 gram of water by 1°C. To illustrate, raising the temperature of 100 grams of water by 2°C would necessitate 200 calories (100 grams × 2°C = 200 cal). The calorie is also used in a dietary context, where it is referred to as the food calorie or kilocalorie (kcal), which is equal to 1000 calories.
It's important to differentiate that degrees Celsius and degrees Fahrenheit are units used to measure temperature, not heat energy.