quEstions 19 to 21 ArE BAsED on thE ConvErsAtion you hAvE just hEArD、 A．BECAusE thEy wAnt to sEll CAntEEns.
B、BECAusE thEy wAnt to EDuCAtE thE tourists ABout pArk ConDitions.
C．BECAusE thE tourists mAy gEt siCk or DiE From DEhyDrAtion.
D．BECAmE thE tourists mAy gEt lost.