Mildew is a fungus that grows in wet areas and can slowly grow from microscopic to large stains in showers and sinks. researchers are studying different sprays that could be used to slow down the growth of mildew. they set up different showers that are exactly the same and expose them each to water with the same microscopic amount of mildew. they then spray some showers with mildew-preventing sprays and observe how fast mildew grows over time. which shower would most likely be the control group in this study? a. the shower sprayed with many test sprays b. the shower not exposed to any mildew at all c. the shower not sprayed with any mildew-preventing spray d. the shower sprayed with a test spray that is already known to work

Keeping in mind the life cycle of bacteriophages, consider the following problem: during the reproductive cycle of a temperate bacteriophage, the viral dna inserts into the bacterial chromosome where the resultant prophage behaves much like a trojan horse. it can remain quiescent, or it can become lytic and initiate a burst of progeny viruses. several operons maintain the prophage state by interacting with a repressor that keeps the lytic cycle in check. insults (ultraviolet light, for example) to the bacterial cell lead to a partial breakdown of the repressor, which in turn causes the production of enzymes involved in the lytic cycle. as stated in this simple form, would you consider this system of regulation to be operating under positive or negative control?