A white solid can be purified from lemon juice. This solid tastes sour. When placed into water the solution conducts electricity and has a pH of 3.0. The solution turns litmus paper red. When the white powder is reacted with sodium hydroxide, a different white powder is formed which tastes salty. What kind of substance is the original white powder isolated from lemon juice?
A an acid
B a base
C a salt
D an enzyme