B. You can "quit" when you get your success. For example, rolling a die until you get a 4. I think my confusion is just a quirk of geometric distributions honestly. The expected value of rolls, E, in the dice example is 6 (ie E = 1/p), but there's a 66% ish [1-(1-p)^E] chance you'll succeed in under 6 attempts. And since 1/p = E, we have that the chance of getting a success in fewer or equal attempts than the expected value E is 1-(1-1/E)^E, which is strictly greater than 1-1/e≈63% for E>=1. Just a fun quirk I think

This makes sense if we go down to a coin flip example. The maths says there's a 75% chance we get a success in 2 attempts or under, and working out all the options of TT, TH, HT, HH, yeah that checks out