answer: #Person1# says scientists have discovered a new AIDS vaccine but #Person2# thinks the best prevention is to keep yourself clean.
documents: #Person1#: I hear scientists in the US have discovered a new AIDS vaccine. 
  #Person2#: Does it work? 
  #Person1#: I don't know. The report says it is better than the old vaccines. 
  #Person2#: Don't count on it. I think the best way to prevent AIDS is to keep yourself clean by having clean sex and keeping a regular sex partner. 
  #Person1#: Right. That's why doctor say AIDS prevention means cleanness.