In the following question, a series of letters is given. Some letters have been removed in these series, and they are in the options given below the series in the same order as they should be. Study the given series carefully out of the four alternatives given below, and find the one that best fits in place of the missing letter of the series.
a b c a __ b c a a b __ c a __ b b c __ a
1
b b a a
2
a b a c
3
a b b a
4
c c a a