Vector quantities require magnitude and direction

Steps:

• Define vector quantities as those with both magnitude and direction, unlike scalars with only magnitude.
• Evaluate option A: mass measures amount of matter, no direction.
• Evaluate option B: temperature measures thermal energy level, no direction.
• Evaluate option C: weight is gravitational force, has direction (downward).
• Evaluate option D: average speed measures distance over time, no direction (unlike velocity).

Why C is correct:

• Weight is a force, and forces are vectors per Newton's laws, requiring magnitude (15 N) and direction.

Why the others are wrong:

• A: Mass is a scalar quantity, defined solely by magnitude in kilograms.
• B: Temperature is a scalar quantity, measuring intensity without direction.
• D: Average speed is a scalar, as it lacks directional component (velocity is the vector form).

Final answer: C