Answer:
Option C
Explanation:
Clearly, the first, second, third, ... letters of the series are respectively moved two, three, four, .. steps forward to obtain the successive terms of the series. Thus the fifth term in the series must be a letter which is five steps ahead of J ie., O. While the sixth term of the series must be a letter six steps ahead of O ie., U.
Hence the answer is O, U ie., (c).