A researcher surveyed 100 elderly people. For each person the researcher conducted a questionaire that measures their level of happiness (on a scale from 1 to 20). The researcher also asked each person how many medications they take per week. The correlation coefficient between these two variable was calcualted to be -0.67. According to this information .... a) we can conclude that the number of medications an elderly person has to take negatively impacts their level of happiness. b) we can conclude that an elderly person's level of happiness has a negative impact on the number of medications they have to take weekly. c) we can conclude that if we want elderly people to have more happiness in their lives, they should take more weekly medications. d) we cannot conclude that either variable is causing a change in the other variable because this is an observational study