Concept:Vectors are physical quantities that require both magnitude and direction for their complete description, whereas scalars have only magnitude.
Explanation:Consider each pair of quantities separately.
Option A: speed is a scalar, while displacement is a vector, so this pair is not made up of vectors.
Option B: mass is a scalar, while force is a vector, so this pair is also incorrect.
Option C: displacement measures the shortest distance in a specified direction, and acceleration measures the rate of change of velocity in a given direction. Both are vectors.
Option D: momentum is a vector, but length is a scalar, so this pair is not correct.
Therefore, the only pair where both quantities are vectors is displacement and acceleration.
Answer:C. displacement and acceleration