#### Answer

It would be best to report a person's weight in kilograms.

#### Work Step by Step

It would be best to report a person's weight in kilograms.
A typical person's weight could be about 70 kg. The number 70 is quite comfortable for people to work with and understand. We have a feeling for the number 70. It is not a huge number or a tiny decimal number. If we use kilograms to report a person's weight, we will be able to use a number which is quite comfortable to work with.
If we use grams to report the person's weight, the weight would be 70,000 grams. The number 70,000 is quite large, so it is quite difficult to work with and hard for us to understand.
If we use milligrams to report the person's weight, the weight would be 70,000,000 milligrams. The number 70,000,000 is very large, so it is difficult to work with and very hard for us to understand. We don't have a feeling for the number 70,000,000. It just feels like a really huge number.