Determine whether each study described below is observational or designed, and explain your reasoning. Complete parts (a) and (b) below. (a) A high school biology student provides one colony of ants with a particular brand of ant food, and another colony with a different brand, and measures the size of each colony over the course of a month. 0 A. A designed study because the analyst controls the specication of the treatments and the method of assigning the experimental units to a treatment 0 B. An observational study because the analyst simply observes the treatments and the response on a sample of experimental units 0 c_ An observational study because the analyst controls the specication of the treatments and the method of assigning the experimental units to a treatment 0 D. A designed study because the analyst simply observes the treatments and the responses on a sample of experimental units (b) Intrastate trucking rates are compared before and after governmental deregulation of prices charged, with the comparison also taking into account distance of haul, goods hauled, and the price of the diesel fuel. 0 A_ An observational study because the analyst simply observes the treatments and the response on a sample of experimental units 0 B. A designed study because the analyst controls the specication of the treatments and the method of assigning the experimental units to a treatment 0 c_ A designed study because the analyst simply observes the treatments and the responses on a sample of experimental units 0 D. An observational study because the analyst controls the specication of the treatments and the method of assigning the experimental units to a treatment