1807年，世界上第一艘汽船“克莱蒙”号的建造者是（    ）

a、b都是不为0的自然数，已知a×$\frac{2}{3}$=b×$\frac{3}{4}$，则a＞b．（判断对错）

阅读判断。根据短文内容，判断下列句子的正与误。

Long long ago, there was no paper in the world. People had to write characters(汉字) in bamboo slips or stones.Then there was a man named Cai Lun who was a Chinese man. He made people use all kinds of things to invent paper. From then on, people can use paper to write on. Paper is a great invention. We always remember the great inventor Cai Lun. Nowadays paper is very useful in our work, study and our life.It really means a lot to human beings

CO₂和O₂是自然界中生命活动不可缺少的两种气体，下列说法正确的是 (        )