Unsigned real number X. Lowest number representable should be 0, nothing stops it from being 0, and restrict it to 0.00043 or something. Hence, A and B eliminated.
Max number representable $2^{i}$ just looks wrong. What about the bits in f, they'd add up, too. So, C eliminated.
Option D seems reasonable.
Solved it under 30 seconds.
A proper solution would be to take small values of n, i and f; first put all 0's (for lower limit) then put all 1's (for upper limit). Then do option elimination.
Option D