Two Strings X and Y Are Indistinguishable If

Multiple Choice

Two strings x and y are indistinguishable if:

A) ?*(s, x) = ?* (s, y) , i.e. the state reached by a DFA M on input x is the same as the state reached by M on input y
B) if for every string z ? ?* either both xz and yz are in language A on ?* or both xz and yz are not in A
C) Both above statements are true
D) None of the above