Answer:
a) 針 -> 古 -> 呈 -> 現
針 SHIN, hari - needle
古 KO, furu(i) - old
呈 TEI - offer, present, exhibit
現 GEN, arawa(reru), arawa(su) - present, appear, show
b) 粒 -> 音 -> 明 -> 胆
粒 RYUU, tsubu - a grain
音 ON, IN, oto, ne - sound
明 MEI, MYOU, aka(rui), a(keru) - bright
胆 TAN - gallbladder, courage