以下各项均为臁疮的诱发因素，除了：（）
A.烫伤
B.虫咬
C.皮肤搔抓
D.寒冻
E.湿疮
参考答案：D
No matter how frequently _______, the works of Beethoven still attract people all overthe world.
A．performed
B．performing
C．to be performed
D．being performed
优级纯、分析纯的符号分别是G.R和A.R，而化学纯的符号是C.P。
