单选题 Cet-6-3.19-Exercise.mp3 Questions 19 to 21 are based on the recording you have just heard.19. A) Adults' influence on children.B) The stabilization of the dollar value.C) Abilities of human babies.D) The issuing of government securities.20. A) They are the oldest buildings in Europe.B) They can distinguish a happy tune from a sad one.C) They are part of the Christian tradition.D) They love happy melodies more than sad ones.21. A) Babies' emotions.B) Feelings of betrayal.C) Infants' behaviors.D) Mental stimulation Question 19