It did not occur to me to “check all cases”. Had this been a math problem about the parity of numbers or some such, I would immediately think “well, A can be either even or odd. If A is odd, then …; and if A is even then …; QED”.
However, my conscious thought process went more like “We can’t tell whether Anne is married, since Jack does not have to be married to her if more than three people exist. We don’t know who George is looking at, so the answer must be C.”
For this problem you can also get the right answer by reasoning wrongly: “Jack must be married to Anne, so the answer is A.”
Damn, I got it wrong.
Semi-spoiler below.
It did not occur to me to “check all cases”. Had this been a math problem about the parity of numbers or some such, I would immediately think “well, A can be either even or odd. If A is odd, then …; and if A is even then …; QED”.
However, my conscious thought process went more like “We can’t tell whether Anne is married, since Jack does not have to be married to her if more than three people exist. We don’t know who George is looking at, so the answer must be C.”
For this problem you can also get the right answer by reasoning wrongly: “Jack must be married to Anne, so the answer is A.”