Which of the following observations is found in the Tollens' test for aldehydes?

• A
  The formation of a pink or magenta color upon the addition of the reagent to the sample solution.
• B
  Formation of an $Ag$ layer on the sides of the test tube upon addition and warming of the reagent.
• C
  Formation of a brick-red precipitate upon heating with the reagent.
• D
  Appearance of a red color upon shaking with the reagent.