Which acid in each of the following pairs is stronger?
a. CH₃COOH or ClCH₂COOH
b. O₂NCH₂COOH or O₂NCH₂CH₂COOH
c. CH₃CH₂COOH or H₃NCH₂COOH
d. HCOOH or CH₃COOH
e. CH₃COOH or CH₃CO