Represent 500 grams as a fraction of a kilogram. (1kilogram = 1000 grams)

The correct option is A

1 kg = 1000 g
Hence 500 grams as a fraction of 1 kg = $\frac{500}{1000}$

Cancelling zeros we get,
$\frac{5}{10}=\frac{1}{2}$ (reducing to its lowest terms by dividing numerator and denominator by 5)