If I swap 15 with the last element, then 12 and 16 remain unchanged !!
Then, total elements which change their positions are 6.
If I swap 15 with the first element, then only 16 remains unchanged !!
Hence, in this case the elements which change their positions are 7.
This question is ambiguous as i think it should give the position. But if not given( like here ), i would go with the maximum .i.e, 7.
As in both the case only 16 is constant by any method, we apply and all others (CAN) change their position means they are having the ability to change their positions . Hence I suppose , 7 should be correct .