In a Kirby-Bauer susceptibility test, the presence of a zone of inhibition around disks containing antimicrobial agents indicates __________ .
a. that the microbe does not grow in the presence of the agents
b. that the microbe grows well in the presence of the agents
c. the smallest amount of the agent that will inhibit the growth of the microbe
d. the minimum amount of an agent that kills the microbe in question