2. Kwik, Kwek, and Kwak each lie on exactly two consecutive days of the week and tell the truth the other five days. No two of them lie on the same day. Uncle Donald wants to know which of his nephews ate the candy jar. The nephews themselves know very well which of the three did it. On Sunday, Kwik says it was Kwek. On Monday, Kwik says it wasn't Kwek after all, while Kwak claims that Kwik is certainly innocent. On Tuesday, however, Kwak says that Kwik did it.

Who ate the candy jar?

A) It was Kwik.

B) It was Kwek.

C) It was Kwak.

D) It was Kwik or Kwek, but you can't be sure which of the two.

E) It was Kwik or Kwak, but you can't be sure which of the two.
A2. C) It was Kwak. Of the statements made by Kwik on Sunday and Monday, exactly one must be true. Suppose Kwik spoke the truth on Sunday. Then he lied on Monday and must have also lied on Tuesday. If Kwik spoke the truth on Monday, then he must have lied on Sunday and therefore also on Saturday. The days Kwik lied were thus either Monday and Tuesday, or Saturday and Sunday.

In the same way, we can examine the two statements made by Kwak. The days Kwak lied were either Sunday and Monday, or Tuesday and Wednesday. Since Kwik and Kwak never lie on the same day, there is only one possibility: Kwik lied on Saturday and Sunday, and Kwak on Tuesday and Wednesday.

On Monday, they both spoke the truth. Therefore, Kwek and Kwik are innocent, and Kwak is the one who ate the candy jar.