I'm pretty sure IQ tests don't ask questions like that. They're supposed to measure intelligence, not knowledge (at least in principle¹), and it's obvious that even a very smart person couldn't possibly figure out whether rattlesnakes are dangerous while taking the test, short of knowing that beforehand.

1. Well, many of them do require knowledge of the English alphabet and its order, a few require a reasonable knowledge of English, and I think even with Raven's Progressive Matrices, some explicit knowledge of discrete maths concepts such as exclusive OR and cyclical permutations is very useful.