“不该新观念，吸收是关键”小丽妈妈一直给小丽吃钙片，医生还说小丽缺钙，建议给小丽増服
A．维生素A
B．维生素B1
C．维生素C
D．维生素D
答案：D
题目分析：幼年缺钙会患佝偻病，中老年人和妇女缺钙易得骨质疏松．维生素对人体也有重要的作用，如果缺乏会得相应的缺乏症，如缺维生素D会患骨质疏松、佝偻病等，因为维生素D影响钙的吸收和利用，即使食物营养中含有钙，但由于身体缺维生素D最终会导致缺钙，使得幼年患佝偻病，中老年人和妇女患骨质疏松．因此补钙的同时一定要补充维生素D．
| 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. |
According to the passage, the algae ______ .
A．may not carry on photosynthesis alone
B．supply food to the fungi
C．can’t live separately
D．aren’t recognizable as a species