19. A student notices that when a weight is hung on a spring, the spring stretches. She decides to conduct an experiment to determine the relationship between the amount of weight placed on a spring and the distance the spring stretches. She has five different weights: 25 9,50 9,75 9, 1009, and 125 9. She selects a weight, hangs it on the spring, and
measures how far the spring stretches.
What should be kept constant throughout this experiment?
O the time of day when the experiment is performed
O the distance the spring stretches
the spring that is used
the weight hung from the spring