Four speed-time graphs are shown below. Which graph represents the following cases?
$(i)$ $A$ ball thrown vertically upwards and returning to the hand of the thrower.
$(ii)$ $A$ body decelerating to a constant speed and then accelerating.

(A) $(i)$ Graph $(a)$ represents this case. The ball starts with an initial velocity,experiences constant retardation due to gravity,and its velocity decreases to become zero at the highest point. Thereafter,the ball falls down,and its velocity increases in the opposite direction until it returns to the hand.
$(ii)$ Graph $(d)$ represents the case of a body decelerating (decreasing speed) to a constant speed and then accelerating (increasing speed).