For a single textbook, grams is better but for loads of them - for example, a year's worth - a kilogram.
Kilograms.
It natters what you're measuring, for you kilograms would be better, because 1 kilogram is about 2.2 pounds. A 175 pound man would weigh 79378.66 grams and 79.38 kg so obviously a gram is good for something with a small mass.
grams
Kilograms because 1 kilogram is 1,000 grams and trucks are very heavy.
A boy is typically measured in kilograms, as this is the standard unit for measuring body weight in most contexts. Grams are generally used for smaller weights or items, while kilograms are more appropriate for human weight.
It would be more appropriate to measure 5 math textbooks in grams or kilograms, as they are smaller and more suitable units for measuring the mass of books. Milligrams would be too small a unit for this measurement.
A marker is typically measured by grams. Kilograms are more commonly used for measuring larger and heavier objects.
Kilograms.
It natters what you're measuring, for you kilograms would be better, because 1 kilogram is about 2.2 pounds. A 175 pound man would weigh 79378.66 grams and 79.38 kg so obviously a gram is good for something with a small mass.
Grams, milligrams, kilograms, etc...
grams or kilograms (more often)
You would use grams to measure a keyboard as keyboards are relatively light and grams are more suitable for measuring small objects like electronic devices.
You would measure a boy's weight in kilograms. Grams are more suited for measuring small, lightweight items.
grams
10 grams is the better estimate of the weight of a crayon.
Kilograms would be more appropriate for measuring the mass of a cannonball, as grams are typically used for smaller and lighter objects.
Kilograms because 1 kilogram is 1,000 grams and trucks are very heavy.