I would probably use kilograms.
Newtons.
pounds
grams
kilo-newtons.
Try grams
That depends what aspect of the adult you want to measure: the adult's height, mass, weight, volume, albedo, intelligence (no SI unit for that!), etc.
Pounds
You would use the unit of measurement called "kilograms" or "pounds" to measure the weight of a car.
You would typically use a unit of weight, such as grams or ounces, to measure a cherry.
A millinewton. NOT a gram, which a measure of mass, not of weight.
grams
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Newtons.
pounds
The most appropriate unit of weight for a computer would be in pounds.
ounces
most likely in grams