Answer:
Choices A, B, and C are correct.
Explanation:
Let us look at each of the choices one by one:
A. It is a vector
Yes. Velocity is a vector, or it's a speed with direction.
B. It is the change in displacement divided by the change in time.
Yes. The velocity can be written as
where is the displacement—a vector quantity.
C. It can be measured in meters per second.
Yes. The units of velocity are m/s, but also with a unit vector indicating the direction.
D. It is the slope of the acceleration vs. time graph.
Nope. The velocity is the slope of displacement vs. time graph.
Hence, only choices A, B, and C are correct.