The PK₁,pK₂,and PK_R for the Amino Acid Arginine Are 1 $\alpha$

The pK₁,pK₂,and pK_R for the amino acid arginine are 1.8,9.0,and 12.5,respectively.At pH 7.0 arginine would be charged predominantly as follows:

A) " $\alpha$ -carboxylate 0, $\alpha$ -amino 0,guanidino +1,net charge +1"
B) " $\alpha$ -carboxylate +1, $\alpha$ -amino 0,guanidino -1,net charge 0"
C) " $\alpha$ -carboxylate +1, $\alpha$ -amino −1,guanidino −1,net charge −1"
D) " $\alpha$ -carboxylate −1, $\alpha$ -amino +1,guanidino +1,net charge +1"
E) " $\alpha$ -carboxylate −1, $\alpha$ -amino 0,guanidino +1,net charge 0"