放射性防护三原则是什么?
参考答案:
(1)控制受照射时间;
(2)增大与辐射源间的距离;
(3)在人与辐射源之间加上适当的屏蔽物。
—My car _____ twice this month.
—I'm sorry to hear that.[ ]
A. has been broken in
B. was broken in
C. has been broken into
D. was broken into
在制剂中作为金属离子络合剂使用的是
A.碳酸氢钠B.焦亚硫酸钠C.依地酸二钠D.碳酸钠E.氢氧化钠