100 mL of a 0.1 M CH₃COOH is titrated with 0.1 M NaOH solution. The pH of the solution in the titration flask at the titre value of 50 is:
[pKa(CH₃COOH)=4.74]

A. 2.37
B. 4.74
C. 1.34
D. 5.74