下列物质分类正确的是（ ）
A．Cu（OH）2难溶于水，属于非电解质
B．SO2能与碱反应生成盐和水，属于酸性氧化物
C．NH4Cl组成中不含金属离子，不属于盐
D．金属铝易导电，属于电解质并且属于强电解质
A、Cu（OH）2难溶于水，属于电解质，故A错误；
B、SO2能与碱反应生成盐和水，属于酸性氧化物，故B正确；
C、NH4Cl组成中不含金属离子，但含铵根离子，属于盐，故C错误；
D、金属铝易导电，不是电解质或非电解质，故D错误；
故选B．
有氧气、氮气、空气、二氧化碳四瓶无色气体，现将它们一一鉴别出来，进行了如下操作，请把内容补充完整．
| 实验步骤 | 实验现象 | 实验结论 |
| 1、先将燃着的木条伸入四瓶气体 | 木条燃烧更旺 | ______ |
| 木条燃烧如初 | ______ | |
| ______ | 该气体是氮气和二氧化碳 | |
| 2、______ | ______ | 该气体是氮气 |
| ______ | 该气体是二氧化碳 |
| Lichens may grow on the bark of a tree in a steaming tropical rain forest, on the bricks of big city buildings, on rocks in hot springs, on wind-swept mountaintops, and in the driest desserts. In the arctic, they provide the principal food for caribou, and they are one of the few plants that grow in Antarctica. They are pioneers, appearing in barren rocky areas and starting the formation of soil in which mosses, then ferns, and then other plants can take root. Lichens are a partnership of two plants — fungi and algae. The lichen body is made up of a network of fungal strands. In the upper layers of these grow groups of algae. The two organisms live together to the benefit of both, a relationship known as symbiosis. The fungi provide support, absorb water, and shelter the tender algae from direct sunlight. The algae carry on photosynthesis and provide the fungi with food. The algae can live independently and are recognizable as a species that grows alone. The fungi, on the other hand, cannot live apart from their partners. They can be placed in known classes of fungi but are unlike any species that lives independently. So definite are the form, color, and characteristics of these double organisms that for hundreds of years, they were classified as one. More than 15,000 "species" were named. If these organisms are classified as separate species, it is difficult to fit them into the existing system of classification. But if they are classified separately, these species of fungi seem rather strange. Lichens are a splendid example of the difficulties faced by taxonomists in classifying species. |
The word "barren" underlined in Paragraph 1 most probably means _______ .
A．lifeless
B．frigid
C．hard
D．uncovered