For what it's worth... pretty much nothing... 
For what it's worth.....he's right nothing....nonetheless, there it is. 
So neither of you was smart enough to realize that the birthday question was ambiguous?
All of the questions are to some extent ambiguous,
To some extent. They are written so that we would give them a wrong interpretation in a casual conversation, but if you really consider what is asked and not what might be meant most of them aren't ambiguous at all.
"Is there a 4th of July in England?" could be taken to mean "do the English celebrate the American Independence Day or something similar?" And in daily life that interpretation would be a bit strange but quite reasonable. But if you read the question ignoring any possible subtexts, there is no ambiguity. Of course there is a 4th of July in England. There is no 34th of July though.
"Some months have 31 days; how many have 28?" In casual conversation this would mean "how many months have
only 28 days?" but by now we have learnt that the questions should be interpreted literally instead of intelligently. We should not add the word "only" to our interpretation.
"Is it legal for a man in California to marry his widow's sister?" This is a tough one. If dead people can be baptised in Utah, maybe they can be married in California. And if I marry two sisters in succession in California and then die, would either marriage be illegal? It is however pretty clear that whoever formulated the question just hoped that I wouldn't realize that if I had a widow I must be dead.
But: "How many birthdays does the average man have?"
Like O-P I "followed the original instructions given by
The Chief,
Pay close attention and consider each question carefully..."
I may not be an average man, but not counting my actual birth day I have had 69 birthdays. I considered answering "one", as I only have one per year, but that would simply have been stupid. A bad test.
