It depends on what you want to measure. If you want its mass you'd use kilograms. If you want its length you'd use metres (or centimetres). Its volume would be in centimetres cubed. (I'm using UK spellings, which are the same as the original French).
Kilogram
Kilometers
what unit of measure is thickness og a ballpen
Due to their small size, you would use millimeters to measure the length of an ant.
Feet if it is a large snake or Inches if it is realtively small.
miles
Pencil lead is very narrow. Millimeter can be used to measure it.
to measure a small trashcan
what unit of measure is thickness og a ballpen
Milliliters.
inches
Millimetre.
if large,pints if small,ounces if medium,cups
inches because there small enough
Due to their small size, you would use millimeters to measure the length of an ant.
Inches or Centimeters would be small enough to measure a teacup.
You can use cups to measure a small can of juice.
gram
Metres; centimetres are too small, kilometres are too large.