Answer- D. 1/8
Imagine it as a normal math problem. If the eight is already the denominator, then you'll just need 2/8ths more. (A.): 3/10 is already too much. (B.): 1/4 won't work because if you add four on top and bottom you'll end up with 5/8. (C.): 3/4 won't work either because you'll end up with 7/8. (D.): 1/8 will work because it already has the denominator, so the denominator stays the same, and you just add 2/8ths, and you're done!