Answer:
Option A. a
Step-by-step explanation:
Motion variables include:
1. Final velocity (vf).
2. Initial velocity (vi).
3. Time (t).
4. Acceleration (a)
5. Distance (x)
Considering the equation given in the question:
Δx = ½(vf + vi) t
We can see that the acceleration (a) is missing in the equation.