Say a b c or d if the answer is something random LIKE 180 then I am not giving brainliest!

Select a graph that have an equation with a < 0

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. they randomly assigned 20 participants to a control group or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. which statistical analysis should be performed to answer the researchers' question?

Graph y ≥ -x^2 - 1. click on the graph until the correct graph appears.