1) electron is an example of a) negative charge b) positive charge c) neutral chrage 2) proton is an example of a) negative charge b) positive charge c) neutral chrage 3) like charges a) attract b) repel 4) un-like charges  a) attract b) repel 5) charges are a) quantized b) negative and positive c) all of the above

排行榜

视觉风格

选项

切换模板

恢复自动保存: