Which of the following is not a vector?

$A$ body can have zero average velocity but not zero average speed. Justify this statement by giving an example.

$A$ motorcyclist drives from $A$ to $B$ with a uniform speed of $30\, km\, h^{-1}$ and returns back with a speed of $20\, km\, h^{-1}$. Find its average speed (in $km\, h^{-1}$).

What is the numerical ratio of average velocity to average speed of an object when it is moving along a straight path?

List two differences in tabular form between speed and velocity. When is a body said to have: $(a)$ uniform velocity and $(b)$ variable velocity? How is the average velocity of a body calculated when its velocity changes at a non-uniform rate?

State whether the following statement is true or false:
Velocity and speed are measured in different units.