Final answer:
To convert 500 grams to kilograms, move the decimal three places to the left which gives you 0.5 kg, so the answer is A. 0.5 kg.
Step-by-step explanation:
To convert 500 grams to kilograms, you need to know that 1 kilogram is equal to 1000 grams. Therefore, you move the decimal three places to the left. So, 500 grams is equal to 0.5 kilograms, which makes the correct answer A. 0.5 kg.