Which One Set of Letters When Sequentially Placed at the Gaps :

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

1. _zy_zxy_yxzx_zyx_xy
   (a) yzxyx                            (b) yxzyz                   (b) xyzzy                 (d) zxyzy
2. b_ac_cc_cb_ab_ac
   (a) bbaac                          (b) cbaba                   (c) abbbc                 (d) aabba