The appropriate label for the slope of this graph is

km/hr
km/hr/s
km/s
km/m
the appropriate label for the slope of this graph is

km/hr
km/hr/s
km/s
km/m

both go with the pic!

The appropiate label for the slope in this graph is km/hr/s

km/hr/s

This graph show about the acceleration for the moving obeject that the acceleration is constant,  (it is always the same acceleration 6 km/h/s). 

acceleration =velocity/time
To compute acceleration we need two points:
(10,60)
(0,0)

aceleration=(60-0)km/h/(10-0)s)=6 km/h/s

Where are the following questions