The energy content of food is commonly expressed in kilocalories; one kilocalorie equals 4184 joules.

• A. 4184 joules
• B. 4.184 joules
• C. 4184 kilojoules
• D. 4184 kilojoules

Answer: (A)

When we talk about the energy in food, we use kilocalories, which are calories scaled by 1000. Since 1 cal = 4.184 J, 1 kcal = 1000 cal = 4184 J. So the energy content expressed in kilocalories corresponds to 4184 joules per kilocalorie, which matches the statement. In other words, 1 kcal is 4184 J (about 4.184 kJ).

The other options mix up the units: 4.184 J would be the energy of one ordinary calorie, not a kilocalorie; 4184 kJ would be 4,184,000 J (about 1000 kcal), and 4184 kilojoules would be 4,184,000 J as well—far larger than a single kilocalorie. For a quick check, a food item with 50 kcal has about 50 × 4184 J ≈ 209,200 J (about 209 kJ).