Letter and Symbol Series Questions

• — stt — tt — tts —
• cc — ccbc — accbcc — c — b
• ZYX—W—YZZ—XWWXY —
• _aa_ba_bb_ab_aab
• — bbm — amb — m — a — bb
• — n m m n — m m n n — m n n m —
• – op – mo – n – – p n m o p –
• nc—dcn—cddc—n—ddcnn—d
• a _ ab_bcbc_caca_
• bcde ebcd debc cdeb ?
• ab__dda__ccd__bb__d__
• ccbab _ caa _ bccc _ a _
• a _ b _ ca _ b _ c _ a _ cc
• b _ ac _ cc _ cb _ ab _ ac
• _ _ babbba_a_ _
• a_baa_baa_ba
• _ _ aba _ _ ba _ ab
• Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it? BR _ _ NB _ O _ NB
• SH _ ELAS _ EELA _ HEELA SHEE _ A
• aa__a__b__abaa__