Determine whether the study is an experiment or an observational​ study, and then identify a major problem with the study. A medical researcher tested for a difference in systolic blood pressure levels between male and female students who are 12 years of age. She randomly selected four males and four females for her study. This is an ▼ because the researcher ▼ does not attempt to modify applies a treatment to the individuals. What is a major problem with the​ study? A. There is no​ blinding, which has a high chance of leading to bias. B. The sample includes male and female students. C. This is a convenience sample with voluntary​ response, which has a high chance of leading to bias. D. The sample is too small.