Answer:
洋 YOU - ocean, foreign, western
差 SA, sa(su) - difference, hold (umbrella), thrust
奥 OU, oku(ru) - interior
胆 TAN - gallbladder, courage
生 SEI, nama - live, raw, alive
All take 大 (DAI, oo(kii) - big) in front to make a word, but only 奥 uses the "Oo" reading (oooku); the others are all "Tai/Dai-":
大洋 TAIYOU - ocean
大差 TAISA - a large difference
大奥 oooku - the female residence in a Japanese castle
大胆 DAITAN - bold, brave
大生 DAISEI - University student