What is the average velocity of the car? explain

Well, part of 'velocity' is the direction of the motion, and the graph doesn't give us any information about the direction.  So the best we'll be able to do is find the average SPEED of the car.

On a distance/time graph, the speed is just the slope of the line. Since this graph is a straight line, it doesn't matter which points along the line you choose ... the answer will always be the same.

Average speed = (distance covered) / (time to cover the distance)

Let's use the ends of the line ... the origin, and the point at the top.

On the left side of the graph, we see the label 'Distance (m)', and I don't know what 'm' stands for.  It could be 'miles' or 'meters'.

Anyway, the point at the top of the line shows that the car covered a distance of 25.0 'm' in 10.0 s of time.

Average speed = (25 m) / (10 s)

Average speed = (25/10) m/s

(I'm pretty sure that 'm' means 'meters' and 's' means 'seconds'.)

option number c is the right answer.

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min