Which quartet of carboxylic acids has increasing acidity from left to right?
a. Methanoic acid, Ethanoic acid, Propanoic acid, Butanoic acid
b. Butanoic acid, Propanoic acid, Ethanoic acid, Methanoic acid
c. Ethanoic acid, Methanoic acid, Butanoic acid, Propanoic acid
d. Propanoic acid, Butanoic acid, Methanoic acid, Ethanoic acid