职业性致癌物包括（）。
A.确认致癌物
B.可疑致癌物
C.潜在致癌物
D.动物致癌物
E.A、B、C三项
参考答案：E
A professor in Beijing University, believed that business inthe market economy must __ the right balance
between theirpursuit of profits and the needs of customers. [ ]
A. regain
B. assume
C. strike
D. decline
套管裂纹有什么危害性？
