What is the slope of a velocity (speed) vs time graph? Acceleration
Positive slope = positive acceleration (getting faster)
Negative slope = negative acceleration (getting slower)
Horizontal Line (0 slope) = no acceleration (constant speed)
If the horizontal line is on the X axis, it is a constant speed of 0 so you are at rest.
If the horizontal line is not on the axis, it is a constant speed moving forward (+) or backwards (-)
A to B: Positive Acceleration for 3 seconds (aka speeding up) from a speed of 0m/s to 4m/s
B to C: Constant speed of 4m/s for 3 seconds
C to D: Positive Acceleration for 2 seconds (aka speeding up) from a speed of 4m/s to 6m/s
D to E: Negative Acceleration for 3 seconds (aka slowing down) from a speed of 6m/s to 0m/s