It is unlikely that Sandra left the milk. There is almost no chance that Emily is a mouse. It is impossible that Greg is white. It is likely that if 'Emily is a mouse and Greg is white' then Mary put down the apple. It is almost certain that if 'Emily is a mouse' or 'Sandra left the milk' or both then John dropped the apple. We doubt that if 'Emily is a mouse and Sandra left the milk' then Brian is a lion.
We doubt that 'Sandra left the milk' or 'Greg is white' or both.
We doubt that 'Sandra left the milk' or 'Greg is white' or both.
It is almost certain that 'Sandra left the milk' or 'Greg is white' or both.

  and(A,B) :- A,B.
  or(A,B) :- A;B.
  nand(A,B) :- not(and(A,B)).
  nor(A,B) :- not(or(A,B)).
  xor(A,B) :- or(A,B), nand(A,B).

  %hop0
  0.2::factA.
  0.02::factB.
  0.0::factC.
  %hop1
  0.7::factX:-and(factB,factC).
  0.95::factY:-or(factB,factA).
  0.2::factZ:-and(factB,factA).

  %hop2
  conclusion:-or(factA,factC).

  query(conclusion).
  
'Sandra left the milk' or 'Greg is white' or both.