Centimeters
A scientist would most likely use a ruler or caliper to measure the length of a nail or other small object. These tools provide accurate measurements in centimeters or inches.
A scientist would typically use a ruler or measuring tape to measure the length of a fish. They would place the measuring tool along the fish from the tip of its mouth to the end of its tail to get an accurate measurement.
grams (for their mass), centimetres (for length), millimetres (for thickness/height), possibly Mohs scale for hardness.
The most appropriate unit to measure a pencil would be centimeters or inches. These units are commonly used for measuring small objects like pencils due to their size. A standard pencil is typically around 17.5 centimeters or 6.9 inches long.
Pencil lead is very narrow. Millimeter can be used to measure it.
a ruler!
A ruler would do the trick.
You would measure it in centimeters.
Centimeters
If you have to measure the pencil to a couple decimal places i would suggest a micrometer and a dial caliper.
Centimeters
A ruler or tape measure.
length
Mm
The length of a pencil. your waist/chest measurement the dimensions of a table
Centimetres, millimetres or inches would be most appropriate for measuring the length of a ruler.
An average pencil when new would be around 15 centimetres long.