5. a student placed a disk of filter paper in each of the following solutions: disinfectant 1, disinfectant 2, disinfectant 3, and distilled
water. while the four disks were soaking in their respective solutions, she streaked a sterile nutrient agar dish with a culture of e. coli
bacteria. then, she placed each disk carefully onto the nutrient agar dish, placed the lid on the dish, taped it shut, and incubated the dish
at 37°c for several days. the diagram shows how the nutrient agar dish looked on day 1 and day 4. the shaded portion of the plate on
day 4 indicates the bacterial growth.
what is the control in the experiment?
a. disk soaked in disinfectant 3
b. disk soaked in disinfectant 1
c. disk soaked in disinfectant 2
d. disk soaked in distilled water

Which statements best describe the differences or similarities between a comparative investigation and an experimental investigation? check all that apply. experimental investigations are best for showing cause-and-effect relationships, while comparative investigations do not necessarily show this type of relationship. comparative investigations are often impractical and unrealistic, while experimental investigations are the most practical and realistic kinds of investigations. comparative investigations allow for the use of a wide range of variables but do not have a control group, while experimental investigations involve variables that can be controlled. both experimental investigations and comparative investigations are designed to answer scientific questions. both experimental investigations and comparative investigations focus on making observations rather than collecting new data.