题目

下列命题中，逆命题错误的是（） A . 平行四边形的对角线互相平分 B . 有两对邻角互补的四边形是平行四边形 C . 平行四边形的一组对边平行，另一组对边相等 D . 两组对边分别相等的四边形是平行四边形 答案：CBroken rubber bands and flat tires requiring replacement could soon be a thing of the past．French researchers have developed a new kind of rubber that can repair itself when broken．The new rubber is made from widely available materials including vegetable oil and a common industrial chemical．All the materials are considered safe to the environment and can be easily reused．The best part is that the new rubber can be repaired and used again and again without losing its strength or ability or stretch．When cut, the rubber can be made new again, simply by pressing the two broken ends back together．The product can be repaired at room temperature, around twenty degrees Centigrade；other self-healing materials require higher temperatures for repair．Traditionally, rubber substances are made from huge molecules（分子）connected by strong chemical links, or bonds．The new rubber is made of smaller molecules．The molecules are linked together using hydrogen bonds．When connected in this way, the molecules act like one long molecule, forming what is called supramolecular networks（超分子网）．When the rubber is cut, the molecules attempt to connect with whatever molecule is near them．When pressed together, the molecules are able to repair themselves at the molecular level, making the repaired rubber like new．However, time is an important element in the process．If the broken ends are not brought together quickly, a repair is not possible．This is because molecules will form bonds with molecules on their own side．The inventors say the surfaces of the rubber can be repaired within a week of being separated．The rubber is the creation of scientists at the Industrial Physics and Chemistry Higher Education Institution in Paris．The organization is part of France's National Center for Scientific Research．The new material is described in greater detail in the research publication Nature．【小题1】According to the introduction, which of the following is NOT the advantage of the new rubber?A．It can be made as easily as common rubber．B．It is environmentally-friendly．C．It can repair itself at room temperature．D．It is made of smaller molecules．【小题2】What does the 5th paragraph mainly tell us?A．Why the new rubber is unique．B．Why the new rubber can repair itself．C．The new rubber is made from huge molecules．D．The new rubber is different from the common rubber．【小题3】If we want to know more about the technology of this kind of new rubber, where can we get the information?A．In the researchers' diary．B．In a guide book．C．In a research magazine．D．In a newspaper．