Explanation:
the graph is like a rough movie of what the water balloon does :
first it goes up a little bit, then it stays a little bit more of less at the same height, and then it drops.
to answer the questions we really only follow the explicit meaning of the graph line :
A
during the interval of 0 and 2 seconds.
B
during the interval of 2 and 4 seconds.
C
the height of the water balloon decreases the fastest during the interval of 4 and 6 seconds (it decreases by almost 40 ft in 2 seconds).
in the intervals between 6 and 8 seconds and 8 and 10 seconds it only decreases by 20 ft in 2 seconds.
D
after 10 seconds the water balloon hits the ground (height 0 ft). from there on it will stay on the ground (0 ft). therefore, at 16 seconds it will be on the ground (0 ft).
FYI - at least on Earth this will not happen in real life : there will never be a period of time > 0 seconds where the balloon will stay flat in the air (unless something is holding it up). and any falling object (except an object with a large air resistance like a feather) will speed up during the fall and not slow down.