题目

The expression “down to earth” means being open and honest. It is easy to get on with some one who is down to earth. A down-to-earth person is the opposite of someone who acts important or proud. Down-to-earth people could be important members of society. But they do not consider themselves to be better than others who are less important. A person who is filed with his own importance and pride is said to have his nose in the air. Americans use another expression that is similar in some ways to down to earth. The expression is both feet on the ground. Someone with both feet on the ground is18．下列物质的性质中，属于化学性质的是（　　）A．干冰易升华B．酒精易挥发C．氢气可燃烧D．CO2能溶于水