题目

Students can improve their compositionsby (polish) them. 答案：【1】polishing甲、乙、丙三人同行，甲受重伤急需输大量血，已知甲的血型为B型，乙为AB型，丙为B型，可以给甲输血的是（　　）A.乙B.丙C.乙、丙都可以D.乙、丙都不可以