During the titration of a mixture of `Na_(2)CO_(3)` and `NaHCO_(3)` against HCl :
A. Phenolphthalein is used to detect the first end point
B. Phenolphthalein is used to detect the second end point
C. Methyl orange is used to detect the first end point
D. Phenolphthalein is used to detect the first and second end point