自然界只有正、负两种电荷，我们把用绸子摩擦过的玻璃棒带的电荷叫做____ ，同种电荷相互____
— The Lost MH370 hasn't been found so far.— What a pity!
They were shocked at the____(令人恐惧的) news that they had cheated so much money.
家庭日常生活中经常用到的下列物质中，属于纯净物的是 （ ）
