Answer:
a) 柔 -> 柱 -> 素 -> 績
柔 JUU, NYUU, yawa(rakai) - soft
柱 CHUU, hashira - pillar, column, pole
素 SO, SU - element, naked, simple
績 SEKI - achievements, spinning
b) 妄 -> 如 -> 吐 -> 堤
妄 MOU, BOU - without reason, without authority
如 JO, NYO - equal, like, as, as if
吐 TOU, ha(ku) - spew, vomit, give vent to
堤 TEI, tsutsumi - bank, embankment, dike