Sleep apnea is a disorder in which you have one or more pauses in breathing or shallow breaths while you sleep, In a cross-sectional study of 440 adults who suffer from sleep apnea, it was found that 264 had gum disease. Note: In the general population, about 17.5% of individuals have gum disease. Complete parts (a) through (c) below. Click here to view the standard normal distribution table (page 1). Click here to view the standard normal distribution table (page 2). Click here to view the table of critical t-values, (a) What does it mean for this study to be cross-sectional? O A. The data were obtained over the course of time and the study was an observational study. O B. The data were obtained over the course of time and the study was an experiment. O C. The data were obtained at a specific point in time and the study was an experiment. O D. The data were obtained at a specific point in time and the study was an observational study. (b) What is the variable of interest in this study? Is it qualitative or quantitative? Explain. Identify the variable of interest. Choose the correct answer below. O A. Whether a person has sleep apnea or not. O B. Whether a person has gum disease or not. O C. Whether a person with sleep apnea has gum disease or not. O D. The proportion of gum disease present in those with sleep apnea