题目

American and British people both speak English, but sometimes it doesn’t seem like the same language. First of all, they sound very different. Often, Americans don’t say all the letters in each word, especially consonants （辅音） like “t” and “d.” For example, Americans may say “I dun no” instead of “I don’t know”. However, the British usually pronounce their consonants more carefully. Also, some letters have different sounds. For example, Americans say the “a” in “half” like the “a” in “cat,” but the British say the “a” in “half” like the 18．关于原子结构及原子核的知识，下列判断正确的是（　　）A．每一种原子都有自己的特征谱线B．α射线的穿透能力比γ射线弱C．γ射线是原子核受到激发后产生的D．放射性元素的半衰期可能与压力、温度有关