（找出与段落无关的句子并写下来）Read the following paragraph and find out the TWO irrelevant sentences.Copy them on the Answer Sheet.An aerosol (气雾剂) product, then, is just a can that has an aerosol mixture inside. With most aerosol cans, the product inside-that is, the cream, or the paint, or whatever-is mixed with a gas. Most of the time the gas that is used is a fluorohydrocarbon(碳氢氟化合物).Almost any gas could be used, and the aerosol would still work. But fluorohydrocarbons are used because they are inert-or inactive. We feel being inactive is safer. That means they don't have any effect on the product inside the can. To take an example, if we mix whipping cream or cheese together with a simple gas-such as oxygen--then the oxygen will immediately start to act on the product, and little by little the oxygen will ruin the product. Cheese mixed with oxygen becomes bad within a few days. That would be dangerous if it is eaten. But, by mixing the product with a fluorohydrocarbon, the product will not change and can be stored for a long time.