I don't even have 2012 installed yet, so I did some research, and found:
"A folder contains one or more projects and environments in the SSISDB catalog."
but the answer to the QOTD says zero.
so who is right?
You have to create the folder before you can push a project to it. When you create the folder it has zero projects in it, and if you create a few folders at the start, they can still exist with zero projects in them.
What does the word "should" mean? It doesn't mean the same as "can", that's for sure. Could the use of "should" with "one or more" versus the use of "can" with zero or more" be an attempt to produce a nasty trick question? If not, why are the two words used? Does the author think "should" means "must always"?
Both "a folder should contain one or more..." and "a folder can contain zero or more..." are correct - the whole point of a folder is to contain projects and environments, so it should contain a project; but they don't have to contain one all the time, that would make creation too complex, which is why "should".
The same applies to "catalog should have one or more folder" and "catalog can have one or more folders": both are correct.
I got this one wrong because I picked the wrong selection from each of the two both correct pairs. I suspect that's because of a language difference.