Choice 2 is the correct answer. I'm not sure of how to prove it but it was on the video.

The order of the questions and answers is not necessarily the same in the two sections.

More to the point, this is not a memory test. You won't be asked to remember a mathematical result for which there is no straightforward derivation such as the probability that the Random Contraction Algorithm will find the right answer.  You should know that it's not 1, though.

The hardest mathematical result that I expect you to be able to figure out yourself is the probability that a Bloom filter slot is 1/0 after some sequence of insertions.  The formula may look difficult, but it's elementary probability, which you should know.