Table 203 the Following Data Were Obtained from a Broth Dilution

Table 20.3 The following data were obtained from a broth dilution test:
$$\begin{array} { | c | l | } \hline \text { Concentration of Antibiotic X } &{ \text { Growth } } \\\hline 2.0 \mu \mathrm { g } / \mathrm { ml } & - \\\hline 1.0 \mu \mathrm { g } / \mathrm { ml } & - \\\hline 0.5 \mu \mathrm { g } / \mathrm { ml } & - \\\hline 0.25 \mu \mathrm { g } / \mathrm { ml } & + \\\hline 0.125 \mu \mathrm { g } / \mathrm { ml } & + \\\hline 0 & + \\\hline\end{array}$$ Bacteria from the 0.25 ?g/ml tube were transferred to new growth media containing antibiotic X with the following results:
$$\begin{array} { | c | l | } \hline \text { Concentration of Antibiotic X } & { \text { Growth } } \\\hline 2.0 \mu \mathrm { g } / \mathrm { ml } & - \\\hline 1.0 \mu \mathrm { g } / \mathrm { ml } & + \\\hline 0.5 \mu \mathrm { g } / \mathrm { ml } & + \\\hline 0.25 \mu \mathrm { g } / \mathrm { ml } & + \\\hline\end{array}$$ The data in Table 20.3 show that these bacteria

A) were resistant to 1.0 ?g/ml at the start of the experiment.
B) were killed by 0.5 ?g/ml of antibiotic X.
C) are pathogenic.
D) were killed by 0.125 ?g/ml of antibiotic X.
E) developed resistance to antibiotics.