Which of the following measurements correctly uses a metric prefix?

• A. 5 km
• B. 12 gal
• C. 3.2 ft
• D. 200 lbs

Answer: (A)

Verified step by step guidance

1. Understand that a metric prefix is a prefix that precedes a unit of measure to indicate a multiple or fraction of the unit, such as kilo- (k), centi- (c), milli- (m), etc.
2. Review each option to see if it uses a metric prefix combined with a metric unit: for example, 'km' stands for kilometers, where 'kilo-' is a metric prefix and 'meter' is the metric unit.
3. Check the units in the options: 'gal' (gallons), 'ft' (feet), and 'lbs' (pounds) are not metric units and do not use metric prefixes.
4. Identify that '5 km' uses the metric prefix 'kilo-' with the metric unit 'meter', making it a correct use of a metric prefix.
5. Conclude that the measurement '5 km' correctly uses a metric prefix, while the others do not because they are either non-metric units or lack metric prefixes.