When you say "most likely", do you mean slightly more likely than the other options, or you believe that's more than likely the answer?
It's the most likely fit based on what we know and hypothesise at this point. This may be different next year or even next week. Some of the maths requires 11 or 12 dimensions. My maths isn't strong ernough to follow, but the discrepancy is something to do with us not being able to understand time like dimensions.
It's still entirely possible that there is only one universe. We have no idea how to test the multiverse theories.