Fiy people with severe headaches are randomly divided into two groups. One group is treated weekly with laughing sessions and an exercise regimen. The other is treated weekly with exactly the same exercise regimen, but no laughing sessions. Atter one year, both groups are questioned about their severe headaches. a. Identify the response variable and the explanatory variable. b. Was this an observational study or an experiment? Explain why. n. The response variable is l and the explanatory variable is E b. Choose the correct description of the study. O A. The study is an observational study because the researchers cannot control the response variable aer 1 year. 0 B. The study is an experiment because the researchers assign subjects to certain experimental conditions and observe the outcomes on the response variable. 0 C. The study is an experiment because the researchers cannot control the response variable alter 1 year. O D. The study is an observational study because the researchers only observe values of the response and explanatory variables