Consider the Pathway for the Synthesis of the Amino Acid

Consider the pathway for the synthesis of the amino acid arginine in Neurospora: $\begin{array}{ll}&A R G-E&&A R G-F&&A R G-H\\\text { ornithine }& \rightarrow &\text { citrulline } &\rightarrow& \text { argininosuccinate } &\rightarrow&\text { arginine }\end{array}$
Mutant strains of Neurospora may carry one or more mutations.Neurospora mutant strain b is grown on minimal media plus supplements as shown.Growth is shown by (+) and no growth is shown by (o) . $~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\underline{ Supplements }$
$\begin{array}{cccccc}\begin{array}{c}\text { mutant } \\\text { strain }\end{array} & \text { nothing } & \text { ornithine } & \text { citrulline } & \begin{array}{c}\text { arginino- } \\\text { succinate }\end{array} & \text { arginine } \\\text { a } & 0 & 0 & 0 & + & + \\\text { b } & 0 & 0 & + & + & +\end{array}$ What can you conclude from these data?

A) Strain a has only one mutation and it is in ARG-E.
B) Strain b has only one mutation and it is in ARG-H.
C) Strain a has a mutation in ARG-F and strain b has a mutation in ARG-E.
D) Strain b has mutations in ARG-E, ARG-F, and ARG-H.