23) On an island of scoundrels (who always lie) and knights (who always tell the truth), an explorer meets four inhabitants of the place and asks them what kind they are. The answers he gets are as follows:

(i) "we are all four scoundrels"; (ii) "no, there is only one knight among us"; (iii) "no, there are exactly two"; (iv) "I am a knight". How many of the four are knights?
(A) 1
(B) 2
(C) 3
(D) 4
(E) it is not possible to deduce.
23) The answer is (E). (i) is certainly a knave (a knight could not lie by saying they are all knaves), and the statements of (ii) and (iii) are contradictory, so at least one of them is a knave. However, it could be that (ii) is the only knight (in which case (iv) would lie as a knave), or it could be that (iii) is a knight (in which case (iv) would tell the truth, being a knight).