Answer:
b. a proton donor.
Explanation:
An acid can be defined as a substance that produces hydrogen ions or H+ protons when dissolved in water, according to Arrhenius
\(HCl -> H^{+} + Cl^{-}\)
It, also, can be defined as a molecule or ion which gives or donates a H+ protons when dissolved in water, according to Bronsted y Lowry
\(H^{+} + H_{2}O -> H_{3}O^{+}\)
And, finally, according to Lewis, an acid can be defined as any compound that can accept a pair of electrons.
