Tollens' test is a classical method to determine if a carbonyl compound is either an aldehyde or ketone. Which of the following statements is true regarding this method?
A. An aldehyde is oxidized to the carboxylate salt and a ketone is unchanged.
B. A positive test for Tollens' test is formation of a silver mirror.
C. Silver ion (Ag+) is reduced to Ag°.
D. Statements A, B and C above are true.
E. Statements A, B and C are not true.