The most appropriate metric unit to measure the mass of a concrete block is kilograms (kg).
Depending on your countries standard unit of measurement but either feet or meters would be the answer.
The most appropriate measure is a metre.
You would use millimeters (mm) to measure the thickness of a house key, as it is a small unit appropriate for measuring such dimensions.
100mL of measuring cylinder is the most appropriate (more than beaker) piece of equipment to measure 85mL of water.
meters
What is the most appropriate instrument to measure
Meters
inches
The most appropriate metric unit to measure the mass of a concrete block is kilograms (kg).
Meters
feet
millimeter
The standard unit to measure mass is kilograms.
kilograms
Centimeter
kilometers