Alphabet Test Questions

In the following question, which one set of letters when sequentially placed at the gaps in the given letter series shall complete it ?
MN_O_NN_M_NO

In the following question, from the given alternative words, select the word which cannot be formed using the letters of the given word.
Biological

A series is given with one term missing. Select the correct alternative from the given ones that will complete the series. PR, VX, BD, ?

A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.
BT, DR, FP, ?

A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.
A, E, I, M, ?

A series is given, with one term missing. Choose the correct alternative from the given ones that will complete the series.

CDE, IHG, KLM, QPO, STU, ?

A series is given with one term missing. Choose the correct alternative from the given ones that will complete the series.
NM, PK, SI, ?

In the following question, which one set of letters when sequentially placed at the gaps in the given letter series shall complete it? a_c_e_b_de