Which relation is a function?

Which of the following could be the graph of the equation y = -2x + 5

Suppose a ball is dropped fromca height of 6ft. it bounces back up but time it bounces, it reaches only 7/10 of its pervious height. what is the total of each height that the ball reaches after 5 bounces

You decide instead to take the train there. the train will take 135 minutes. convert this into hours and minutes.