Can someone explain why is this answer c? i don't understand

You will be galileo perform the experiment to determine if objects with different mass fall at the same, or different, rates in the air and in a vacuum. (refer to the walk-through video to locate the online lab within the online textbook).

Suppose you plot the distance traveled by an object at various times and you discover that the graph is not a straight line. what does this indicate about the object's acceleration?

Achild has maximum walking speed of 1.6 m/s. what is the length of the child's legs? 0.26 m