I dont know how to solve this does anybody?

The speed of a falling object increases at a constant rate as time increases since the object was dropped. which graph could represent the relationship betweent time in seconds, and s, speed in meters per second? speed of a falling object object over time

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Which of the following best describes the figure?