第二章测试1.Cathode rays are deflected (偏转) in an electric field（ ）
A:对 B:错
答案:A
2.STP usually refers to the temperature of 0℃ and the pressure of 101.325 kPa（ ）
A:错 B:对
答案:B
3.Alkali metals are all first period elements（ ）
A:对 B:错
答案:B
4.There are as many electrons outside the nucleus as there are units of positive charge on the nucleus. The atom as a whole is electrically neutral（ ）
A:错 B:对
答案:B
5.X-rays are harmless to the human body（ ）
A:对 B:错
答案:B
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