Yes, if you want to know its mass, that would be the appropriate unit.
I will measure a book with grams
no
you would use a kilogram
A kilogram is a measure of mass therefore a kilogram of lead and a kilogram of feathers have the same mass: one kilogram. They would, however, have different volumes and densities.
Potatoes are sold by the kilogram.
Grams
it would be a gram and if you didn't know a kilogram is equal to 1,000 grams
Kilogram is a measure of weight - so you would use it to weight something. You would probably use it for objects that are large enough to make using grams unnecessary.
Strawberries would be measured in grams or ounces.
use gram, since kilogram is for larger items
A kilogram.
Kilogram.