Inserting The Missing Character Questions

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

PE_NP_ON_EO_

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

r_pr_p_q_r_p

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

b_d_ed_b_c_e

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

gh_i_hi_ig_ii_ _

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 a a b _ a _ b c a a b _ a _ b _ a

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

b_a_c_bc_b_ a