Which SI unit is most appropriate for measuring the diameter of a pencil's eraser?

• A. millimeter (mm)
• B. liter (L)
• C. meter (m)
• D. kilogram (kg)

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the quantity being measured. The problem asks for the most appropriate SI unit to measure the diameter of a pencil's eraser, which is a length or distance.
2. Step 2: Recall the SI base unit for length, which is the meter (m). Other units like millimeter (mm) and centimeter (cm) are derived from the meter and are used for smaller lengths.
3. Step 3: Consider the typical size of a pencil's eraser. It is quite small, usually less than a centimeter in diameter, so using meters would be too large and not practical.
4. Step 4: Compare the options: liter (L) is a unit of volume, kilogram (kg) is a unit of mass, so they are not appropriate for measuring length.
5. Step 5: Conclude that millimeter (mm), which is 1/1000 of a meter, is the most suitable unit for measuring small lengths like the diameter of a pencil's eraser.