A. mcg: This stands for microgram, which is a metric unit of weight. The metric system is the standard for medication dosages and clinical documentation worldwide. B. oz: Ounce is part of the imperial system, not metric. It is used in some contexts but is not appropriate for documenting weight in clinical practice. C. mL: Milliliter is a metric unit of volume, not weight. It is used to measure liquid quantities, such as medication dosages or fluid intake/output. D. lb: Pound is a unit of weight in the imperial system. It is commonly used in the U.S., but not considered a metric unit of measurement.