There is a better than even chance that Greg is a frog. It is unlikely that Bernhard is gray. Chances are about even that Mary left the apple. It is probably not the case that if 'Mary left the apple and Bernhard is gray' then Sumit is thirsty. It is highly likely that if 'Greg is a frog' or 'Mary left the apple' or both then Sandra took the football. Chances are slight that if 'Bernhard is gray' or 'Mary left the apple' or both then Jessica is a mouse.
Chances are about even that either 'Mary left the apple' or 'Sumit is thirsty' but not both.
Chances are about even that either 'Mary left the apple' or 'Sumit is thirsty' but not both.
It is almost certain that either 'Mary left the apple' or 'Sumit is thirsty' but not 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
  0.6::factA.
  0.2::factB.
  0.5::factC.
  %hop1
  0.25::factX:-and(factC,factB).
  0.9::factY:-or(factA,factC).
  0.1::factZ:-or(factB,factC).

  %hop2
  conclusion:-xor(factC,factX).

  query(conclusion).
  
Either 'Mary left the apple' or 'Sumit is thirsty' but not both.