A 50.0-mL sample of 0.10 M HNO2 (Ka = 4.0 × 10⁻⁴ is titrated with 0.12 M NaOH. The pH after 25.0 mL of NaOH have been added is:

A) 3.19
B) 3.61
C) 4.02
D) 4.56