Modern horses have a hoof on their feet. The fossils of their ancestors who have died out had multiple toes that then evolved into a hoof. This means that the a
Organisms that have hooves were more likely to reproduce.
b
Organisms with multiple toes didn't eat as much
c
Organisms with toes were eaten by predators
d
Organisms with hooves were taller and stronger

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?