Hello!
As you can see, C says that the ball hits the ground very briefly. This has nothing to do with the decreasing portion.
B says that the ball is hitting briefly for the second time. Again, this does not relate to the decreasing portion of the graph. It has to do with the graph intersecting with 0.
D says that the ball has reached his maximum height. This would be represented by the apex of the graph but not the decreasing section.
A says that the ball has been thrown and is traveling towards the ground. The graph shows that the ball is traveling towards the ground via the depreciation in the graph. Therefore our answer is A.
I hope this helps!