低熔点铅挡块的组成成分是()
A、铅、铋、铜、锡
B、铅、铋、镉、锡
C、铅、铁、铜、铋
D、铅、铝、钨、铋
E、铅、铝、铋、铜
参考答案：B
今年3月，在韩国首尔举行了第二届核安全峰会，核安全峰会是旨在倡导核安全和打击防范核恐怖主义的全球性峰会。下列关于核能的说法正确的是
A．核能是一种可再生能源
B．核反应堆将核能转化为化学能
C．核电站是利用核裂变释放的核能
D．开发核能即使有核泄漏也是安全的
Questions 27～30
A. Their lecturer-student ratio is not reasonable. B. Their staff is not interested in helping students. C. Their lecture halls are not well equipped. D. Their degrees are not accepted by employers.
