荧光光谱分析，用铂金坩埚溶片时，先要在铂金坩埚底部铺满（），以免金属单质腐蚀坩埚。
A.硝酸锂
B.四硼酸锂
C.溴化锂
D.试样
参考答案：B
If city noises_____from increasing, people _____ shout to be heard even at dinner. [ ]
A. are not kept; will have to
B. are not kept; have
C. do not keep; will have to
D. do not keep; have to
要验证铁、银、铜三种金属的活动性顺序，应选择下列那组物质进行实验（ ）
A．铜、硫酸亚铁溶液、硝酸银溶液
B．铜、氯化亚铁溶液、氯化银
C．银、铜、硝酸铁溶液
D．硝酸银溶液、氯化铜溶液、氯化铁溶液
