LAZARILLO OF TORMES

   And it happened that as we were coming to a place called Almorox    when they were gathering the grapes, a grape picker gave him a bunch as alms.

     He decided that we'd have a picnic so that it wouldn't go to waste, and he did it to please me, too, since he'd kicked and beat me quite a bit that day. So we sat down on a low wall, and he said:

    – Now I want to be generous with you: we'll share this bunch of grapes, and you can eat as many as I do.  We'll divide it like this: you take one, then I'll take one.  But you have to promise me that you won't take more than one at a time.  I'll do the same until we finish, and that way there won't be any cheating.

    The agreement was made, and we began.  But on his second turn, the traitor changed his mind and began to take two at a time, evidently thinking that I was doing the same.  But when I saw that he had broken our agreement, I wasn't satisfied with going at his rate of speed.  Instead, I went even further: I took two at a time, or three at a time; n fact, I ate them as fast as I could.  And when there weren't any grapes left, he just sat there for a while with the stem in his hand, and then he shook his head and said:

    – Lazaro, you tricked me.  I'll swear to God that you ate these grapes three at a time.

    – No, I didn't,– I said. –But why do you think so?

     That wise old blind man answered:

    – Do you know how I see that you ate them three at a time?  Because I was eating them two at a time, and you didn't say a word.

    Anonimous (from a translation by Robert S. Rudder)

Instructions: Press one of the letters (a, b and c). The right answer will be in red.