Martin walked away from his school at a constant velocity for the first 30 seconds. he realized that he had to pick up a book from his friend's house which he had already passed. he turned around and walked to his friend's house at a constant velocity for 10 seconds. he stopped at his friend's house for 40 seconds and then walked away from school again at a constant velocity for the next 20 seconds. which of the following graphs best represents martin's motion? first straight line joins ordered pairs 0, 0 and 30, 25, second straight line joins 30, 25 and 40, 20, third straight line joins 40, 20 and 80, 20, and fourth straight line joins 80, 20 and 100, 50 first straight line joins ordered pairs 0, 0 and 30, 25, second straight line joins 30, 25 and 40, 20, third straight line joins 40, 20 and 80, 20, and fourth straight line joins 80, 20 and 100, 10 first straight line joins ordered pairs 0, 0 and 40, 25, second straight line joins 40, 25 and 80, 25, and third straight line joins 80, 25 and 100, 10 first straight line joins ordered pairs 0, 0 and 30, 25, second straight line joins 30, 25 and 40, 20, and third straight line joins 40, 20 and 100, 50