

Logical implication in action - a poll - RiderOfGiraffes

I submitted a poll, 
http://news.ycombinator.com/item?id=2124808, 
then realised the short-coming that people would see the current voting before casting a vote.<p>Here's a quick experimental hack as an alternative.<p>In the light of a recent article (http://news.ycombinator.com/item?id=2121428) by Tim Gowers about the difficulties some people have with mathematical logic, I wondered what people here would answer to this question.<p>Suppose I have four cards. Each card has a letter on one side, and a digit on the other. I arrange them so that you can see "D", "3", "K" and "4". I then claim that every "D" has a "4" on the other side.<p>Which cards do you need to turn over to see if I'm right?<p>Click on the appropriate link.
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RiderOfGiraffes
Click on your choice:

Just D - <http://www.solipsys.co.uk/new/LogicalImplication.html?D>

Just 3 - <http://www.solipsys.co.uk/new/LogicalImplication.html?3>

Just K - <http://www.solipsys.co.uk/new/LogicalImplication.html?K>

Just 4 - <http://www.solipsys.co.uk/new/LogicalImplication.html?4>

D and 3 - <http://www.solipsys.co.uk/new/LogicalImplication.html?D3>

D and K - <http://www.solipsys.co.uk/new/LogicalImplication.html?DK>

D and 4 - <http://www.solipsys.co.uk/new/LogicalImplication.html?D4>

3 and K - <http://www.solipsys.co.uk/new/LogicalImplication.html?3K>

3 and 4 - <http://www.solipsys.co.uk/new/LogicalImplication.html?34>

K and 4 - <http://www.solipsys.co.uk/new/LogicalImplication.html?K4>

D, 3 and K - <http://www.solipsys.co.uk/new/LogicalImplication.html?D3K>

D, 3 and 4 - <http://www.solipsys.co.uk/new/LogicalImplication.html?D34>

D, K and 4 - <http://www.solipsys.co.uk/new/LogicalImplication.html?DK4>

3, K and 4 - <http://www.solipsys.co.uk/new/LogicalImplication.html?3K4>

All of them - <http://www.solipsys.co.uk/new/LogicalImplication.html?D3K4>

