It is one of the two sums that go to infinity. The other two will end in some sort of sum even though r is > 1 in D and < -1 in B. The answer will likely be quite nasty in both of them, still they will end somewhere.
That leaves with A and C.
A: will converge somewhere - 1 <r <1 converges when that condition about r is true and you can get a sum.
C the one that does not converge anywhere. 4/3 raised to a large power gives a very large number which never gets smaller and the sum is indefinite getting larger and larger as i increases. C is your answer.
