Choose the word that has stress differently from that of the other words. 1.A.cavity B.absent C.important D.illness 2.A.aquarium B.selection C.poster D.semester 3.A.healthy B.material C.serious D.nervous 4.A.medical B.measure C.Record D.disease 5.A.aquarium B.decide C.patient D.material 6.A.material B.poster C.improve D.decide