不会发生恶变的疾病有（）
A.白斑
B.慢性盘状红斑狼疮
C.扁平苔藓
D.口腔红斑
E.复发性阿弗它溃疡
参考答案：E
—Oh, Mrs. Ming, your dress looks nice. Is it new?
—No, I _____ it since two years ago. [ ]
A. had
B. bought
C. have had
D. have bought
龋病原发因素中宿主指（）。
A.牙齿
B.唾液
C.细菌
D.食物
E.时间
