Answer:cart B
Explanation:
For cart A speed is constant therefore there is no acceleration because acceleration is rate of change of velocity
thus there is no net force
For cart B there is change in velocity in the left direction , so there is net acceleration towards left
[tex]Force=mass\times acceleration[/tex]
so there is net force in the left direction
For cart C there is decrease in velocity i.e. negative acceleration or deceleration . Therefore there is a net force towards right which opposes the motion
