Figure 161 -According to the Table and Figure 16

Figure 16.1
$\begin{array}{|l|l|l|l|l|}\hline \text { Mutant Strain } & \text { Medium with: } & \text { Medium with: } & \text { Medium with: } & \text { Medium with: } \\& \text { No ornithine } & \text { Ornithine } & \text { No ornithine } & \text { No ornithine } \\& \text { No citrulline } & \text { No citrulline } & \text { Citrulline } & \text { No citrulline } \\& \text { No arginine } & \text { No arginine } & \text { No Arginine } & \text { Arginine } \\\hline \text { argl } & \text { no growth } & \text { GROWTH } & \text { GROWTH } & \text { GROWTH } \\\hline \text { arg2 } & \text { no growth } & \text { no growth } & \text { GROWTH } & \text { GROWTH } \\\hline \text { arg3 } & \text { no growth } & \text { no growth } & \text { no growth } & \text { GROWTH } \\\hline\end{array}$
-According to the table and Figure 16.1, which enzyme is defective in the strain with the arg2 mutation?

A) the enzyme that converts ornithine to citrulline
B) the enzyme that converts the precursor to ornithine
C) the enzyme that converts the precursor to citrulline
D) the enzyme that converts citrulline to arginine