Nokea
What is it called when base units are combined, such as g/mL for density?
Correct Answer: B
Rationale: The correct answer is B: derived units. When base units (such as grams or milliliters) are combined, as seen in g/mL (grams per milliliter) for density, they form derived units. Derived units measure complex quantities that are derived from combinations of base units. Choice A, 'combined units,' is incorrect as it does not specifically refer to the formation of new units from base units. Choice C, 'base units,' is incorrect because base units are the fundamental units from which all other units are derived, not the combinations of units. Choice D, 'calculated units,' is incorrect as it does not accurately describe the concept of combining base units to form a new unit like g/mL for density.