In the following reaction: HC₂H₃O₂ ⇌ H⁺ + C₂H₃O₂^-, if [HC₂H₃O₂] = 0.28 M and the pH = 5.0, what is K?

A) 3.57 × 10^-10
B) 1.00 × 10^-4
C) 1.00 × 10^-10
D) 3.57 × 10^-4

Draw the Fischer projection of L-valine at a pH of 2.