I suppose you are using an Action Bar, what you described is the normal behaviour of the adapter: when there is the need to display a fragment the next fragments in the list will be pre-loaded (by default, but you can change this). So at first you need A, so it will load just B because there is nothing 'at the left' of the A, when you switch to B, just the C fragment will be pre-loaded because A is already present, finally when you go to C the adapter don't need to pre-load anything because there is nothing 'at the right' of the C and it already has B.
Hope it helps.