If the horses complete the race, from the first to the last, in exactly the order 6, 5, 4, 3, 2 and 1 (corresponding to the number of their jockeys); and if B is the horse that wins the race, then each of the following horses could have been among the top three in the race except:
C
As per the question,the top 3 are ridden by jockeys 6,5 and 4.B is ridden by jockey-6.So from condition (iii), E has to be ridden by jockey-4.Among the top 3, we are only left with jockey 5.But jockey 5 cannot ride C as per condition(iv).Hence option (a)