放射性核素示踪技术用来作为示踪剂的是
A．放射性核素
B．放射性核素标记物
C．泛影葡胺
D．钡剂
E．以上均可
参考答案：A,B
—We should use _____ people and _____ money to do the work better. [ ]
A. less ;less
B. fewest ; less
C. fewer ; less
D. fewer; least
哪种电解质紊乱可危及生命()
A．钠
B．镁
C．锌
D．钙
E．钾
