After Mutagenesis and Screening, You Have Found a Mutant That

After mutagenesis and screening, you have found a mutant that is able to grow in soil with high salt content. Chemical analysis showed that this plant has a decreased amount of Na⁺ relative to normal plants. What kind of mutation do you predict this plant contains?

A) mutation in the plasma membrane sodium channel
B) mutation within the Casparian strip
C) mutation in the tonoplast sodium channel
D) mutation in the metallothioneins
E) mutation in the tonoplast antiporter