It depends on ewhat attribute of the thumb you wish to measure:
Some attributes of possible interest are length, mass, conductivity, tensile strength.
If length, probably centimetre. Millimetre or smaller if you wanted an absurd degree of precision.
grams which unit would you use to measure the mass of a mouse
You would use area. I would use the meter2. Okay
You would use Volume.
Honestly you could use any unit of measure! I would use inches. Thanks Cheezpuffz
You would use either inches or centimeters.
Which unit would you use to measure the water in a full tub?
I would use feet
You would use meters.
grams which unit would you use to measure the mass of a mouse
You would use area. I would use the meter2. Okay
The Unit Used To Measure A Train Can Be Kilometer.
if i were you , i would use kg
You would use Volume.
Feet
to measure a small trashcan
Kilograms
miles