A weak acid (or base) is titrated against a strong base (or acid), volume V of strong base (or acid) is plotted against pH of the solution (as shown in fig).The weak electrolyte (i.e., acid or base) could be:
A. `Na_(2)CO_(3)`
B. `Na_(2)C_(2)O_(4)`
C. `H_(2)C_(2)O_(4)`
D. `CH_(4)(CO OH)_(2)`