Final answer:
Displacement and acceleration are vector quantities requiring both magnitude and direction, while speed is a scalar quantity only requiring magnitude. Velocity is a vector that is similar to speed but also includes direction.
Step-by-step explanation:
Among the options provided, the variables that must include a magnitude and direction, making them vector quantities, are displacement and acceleration. In contrast, variables like speed and time are scalar quantities because they only possess magnitude and lack direction.
Velocity is often confused with speed, but they are distinct; velocity is a vector because it describes motion in a specific direction, while speed is just the magnitude of this motion. Considering the information provided, we can determine that the combination of displacement, velocity, and acceleration contains two vectors (displacement and velocity) and one scalar (acceleration) since acceleration also has a direction associated with it.
When analyzing the kinematic equations relevant to this subject, we identify that acceleration, displacement, time, and velocity are the four variables included. It's worth noting that each of these terms plays a critical role in describing motion in one dimension.