Answer:
a. decrease in speed.
Step-by-step explanation:
According to the given diagram, there is a decrease occur in the speed of the bicycle because the initial speed of bicycle is 4 m/s whereas in the end, they have the speed of 3 m/s. So the speed decreases from 4 m/s to 3 m/s, the bicycle takes more time to reach its destination. There is also acceleration produced due to change in their speed but the acceleration is negative due to lowering of speed.