4. A physics Examination
Poly aluminium ChlorideOnce in a physics examination, Nick finished the first question very soon, while his classmates were thinking it hard. The question was: When it thunders why do we see the lighting first, then hear the thunderrolls? Nick\'s answer: Because our eyes are before ears. Jim’s History Examination Uncle: How did Jim do in his history examination? Mother: Oh, not at all well, but there, it wasn't his fault. They asked him things that happened before the poor boy was born.
聚合氯化铝Water treatment chemicals