Consider the following relation:

arc(a,b). arc(b,b). arc(b,c).

Select all possible answers to the following question (finding some of them might require typing a semicolon and backtracking):

?-arc(X, Y), arc(Y,Z).

a)		X = a, Y = Z, Z = b
b)		X = a, Y = b, Z = c ;
c)		X = Y, Y = Z, Z = b
d)		X = Y, Y = b, Z = c

Consider the following relation:

likes(ann,john). likes(peter,ann). likes(john,john).