Letter Series

In following questions, a sequence of groups of alphabets is provided with one term missing , Choose the missing term from options: 
A, CD, GHI, ?, UVWXY

In each of the following letter series, some of the letters are missing which are given in that order as one of the alternatives below it.Choose the correct alternative:
a _ ba _ b _ b _ a _ b

In the following alphabet series, some alphabets are missing which are given in that order as one of the alternatives below it. Choose the correct alternative:
_ _ babbba _ a _ _

In each of the following letter series, some of the letters are missing which are given in that order as one of the alternatives below it. Choose the correct alternative:
cccbb _ aa _ cc _ bbbaa _ c

In alphabet series, some alphabets are missing which are given in that order as one of the alternatives below it. Choose the correct alternative:
_ baa _ aab _ a _ a

LXF, MTJ, NPN, OLR, ?

What should come next in the series: T,R,P,N,...

Choose the correct option to complete the alphabet series:
ba _ cb _ b _ bab _

ZEA, WFB, TGD, QHG, ?

In following question, a sequence of groups of alphabets is provided with one term missing , Choose the missing term from options:
AB, DEF, HIJK, ?, STUVWX