Physical Quantities Require Magnitude and Unit

Steps:

• Recall that a physical quantity describes measurable properties like length or mass.
• Identify key components: every physical quantity has a numerical magnitude and a unit for standardization.
• Evaluate options: A omits unit, B and C omit magnitude, D includes both.
• Confirm D matches the standard definition in physics.

Why D is correct:

• By definition, a physical quantity is the product of a numerical value (magnitude) and a unit, as per the International System of Units (SI), ensuring precise measurement (e.g., 5 meters).

Why the others are wrong:

• A: Units are essential for magnitude to have meaning; unitless quantities like angles are exceptions but still imply magnitude.
• B: Magnitude is always present as a numerical value; unitless claims ignore core definition.
• C: Magnitude is required alongside the unit for any physical description.

Final answer: D