Gram
Milligrams.
The best unit is a litre.
The best unit for measuring the length of a pencil is inches.
For a desk like one used in schools the best unit would be pounds. Good luck on your measuring!
centimetres
inch
pounds
A millimetre.
kilograms
The best unit of measure to use when measuring the amount of water in a drinking glass is ounces. A liquid measuring cup can be used to measure the ounces of water.
The appropriate unit for weight is a Newton.
The newton. (The kilogram is not a unit of weight or force.)