Cumulative Probability Question - Which Is Correct?

Hello,

In each period (#1 - 10) the probability that an event will happen increases 3% from the period prior. What is the probability that it will happen, or has already happened, in any given period (e.g. in period #3, the probability that the event happens at least once in period 1, 2 or 3)? Is approach 'A' capturing the cumulative nature of it correctly? Is 'A' more correct, or another method? I've attached an example sheet with data for my question. Any help appreciated!

Greg