This question can be solved easily if the relation between the letters within the group is observed. In this series the first letter in all the groups form a series of consecutive letters. Hence, the first letter in the next group is E. The other letters in each group are related as follows.
A^*2, B^*2, D^*2, HB^*2, D^*2, H^*2, PC^*2, F^*2, L^*2, XD^*2, H^*2, P^*2, FHence, the next group is obtained as follows.E^*2, J^*2, T^*2, N.Hence, the next group in the series is EJTN.