Q. In the series_b_a_ba_b_abab_aab; fill in the six blanks (_) using one of the following given four choices such that the series follows a specific order.

Explanation : 

The given series is: _b_a_ba_b_abab_aab
The pattern being followed in the above series is: abb, then aab. Again abb, and then aab, and so on.
The blanks have been highlighted below:
a b b / a a b / a b b / a ab / ab b / aab