Yes, there are many moderators of difficulty.

We had some requirements for the test which included graded difficulty from very easy to very hard to be able to separate out people of different abilities over a regular population.

We were supposed to design the first question so that 100% of people got it correct; to be an easy, practice type question.

Also, you guys aren't even getting to see our hardest questions :D Take a look at http://psych.io/spatial/hard.jpg for example!