Answer:
Instantaneous speed
Explanation:
It is given that, Henry was given this cool toy for his birthday. He can use it to tell how fast someone is going at that moment in time. The toy must calculate the person's instantaneous speed.
Instantaneous speed of an object is defined as the speed at a particular instant. Mathematically, it is given by :
[tex]v= \lim_{\Delta t \to 0}(\dfrac{\Delta x}{\Delta t})[/tex]
Instantaneous speed is a scalar quantity. It does not involve any direction.
So, Henry must calculate the person's instantaneous speed. Hence, the correct option is (d).