Which of the Following Solutions Is a Buffer

Which of the following solutions is a buffer?
I. 50 mL of 0.1 M acetic acid mixed with 25 mL of 0.05 M NaOH
II. 100 mL of 0.1 M acetic acid mixed with 25 mL of 0.5 M NaOH
III. 50 mL of 0.1 M acetic acid mixed with 25 mL of 0.05 M sodium acetate
IV. 50 mL of 0.1 M acetic acid mixed with 25 mL of 0.2 M HCl
V. 50 mL of 0.1 M sodium acetate mixed with 25 mL of 0.05 M NaOH

A) I and III
B) III only
C) I, II and V
D) III, IV and V
E) II, IV and V