The correct option is C A spoon contains a syrup of 15ml.
⇒Milligram(mg) -This unit is used to measure small quantities like 500 milligram(mg) of pills etc.
Hence, option A is correct.
⇒500 gram(g)- 500g is equivalent 0.5 kg and tablets are very small. It is not possible to eat a 500g tablet.
⇒ Milliliter(ml) - This unit is used to measure small volume like 500 Milliliter(ml) of coke or 15 ml of syrup etc. Hence option C is correct.
⇒ 500 liter(l)- This is huge amount of volume. It usually fits into a tank or big container.