下列哪些是我国的安全生产方针（）
A.质量第一
B.安全第一
C.预防为主
D.统筹兼顾
E.综合治理
参考答案：B, C, E
Scientists have achieved a major ___ in the search for a cure for cancer, ____ is good news for those who suffer from cancer.
A．breakthrough; what
B．breakdown; which
C．breakup; that
D．breakthrough; which
下列选项中，用于声明类的继承的关键字是 ( )
A．import
B．implements
C．interface
D．extends
