How does one determine whether a bacterial strain is resistant, susceptible, or intermediate via the Kirby-Bauer disc diffusion method?

A) By comparing each clearing zone with a second plate inoculated with a different known strain of bacteria.
B) By measuring clearing zone size and comparing that to a chart that correlates size of zone of inhibition to susceptibility of bacteria to the drug.
C) By measuring and comparing each clearing zone; the smallest one is the drug to which the bacterial strain is most susceptible.
D) By measuring and comparing each clearing zone; the largest one is the drug to which the bacterial strain is most susceptible.