1)if n is a real number then 2n is also a real number. so look at the choices, which one is not a real number?
2) try and come up with examples where the choices arent correct. for example;
E)it is a perfect square, not necessarily since n=1 gives 2n^2 even but 1+1 is not a perfect square.
doing this will give you the right answer.
you could also notice that because of the 2, 2n^2 is always even no matter what integer n is
2 times any number(integer) is always even