Why? Way too easy. Just because start with a b it does not HAVE to be on here. In fact I think the names you see over and over on other quizzes should NOT be on here. Time to broaden your horizon and not be a one trick wonder.
In other words, there are lots of places that begin with B in Europe - you can't have them all otherwise the quiz would become more like an exam at school. Have some realistic expectations
There's Ben Lomond famously, and plenty of other mountains with the Ben name. Mount Blanc would be under B not M.