Each advance in microscopic technique has provided scientists with new perspectives on the function of living organisms and the nature of matter itself. The invention of the visible-light microscope late in the sixteenth century introduced a previously unknown realm of single celled plants and animals. In the twentieth century, electron microscope have provided direct views of viruses and minuscule surface structures. Now another type of microscope, one that utilizes X rays rather than light or electrons, offers a different way of examining tiny de tails; it should extend human perception still farther into the natural world. The dream of building an X-ray microscope dates to 1895; its development, however, was virtually halted in the 1940"s because the development of the electron microscope was progressing rapidly. During the 1940"s, electron microscopes routinely achieved resolution better than that possible with a visible-light microscope, while the performance of X-ray microscopes resisted improvement. In recent years, however, interest in X-ray microscopes has revived, largely because of advances such as the development of new sources of X-ray illumination. As a result, the brightness available today is millions, of times that of X-ray tubes, which, for most of the century, were the only avail able sources of soft X-rays. The new X-ray microscopes considerably improve on the resolution provided by optical microscopes. They can also be used to map the distribution of certain chemical elements. Some can form pictures in extremely short times; others hold the promise of special capabilities such as three-dimensional imaging. Unlike conventional electron microscopy, X-ray microscopy enables specimens to be kept in air and in water, which means that biological samples can be studied under conditions similar to their natural state. The illumination used, so-called soft X rays in the wavelength range of twenty to forty angstroms (an angstrom is one ten-billionth of a meter), is also sufficiently penetrating to, image intact biological cells in many cases. Because of the wavelength of the X rays used, soft X-ray microscopes will never match the highest resolution possible with electron microscopes. Rather, their special properties will make possible investigations that will complement those performed with light-and-electron-based instruments.
单选题
According to the passage, the invention of the visible-light microscope allowed scientists to ______.
【正确答案】
D
【答案解析】解析：本题考查对文章细节的了解。本题是考对最初的光学显微镜的评价，可从第一段第二句话中得到答案。"The invention of the visible-light micro scope late in the sixteenth century introduced a previously unknown realm of single-celled plants and animals"。
单选题
Why does the author mention the visible-light microscope in the first paragraph?
单选题
Why did it take so long to develop the X-ray microscope?
【正确答案】
B
【答案解析】解析：本题考查对文章细节部分理解的能力。文章第二段详细介绍了X射线显微镜为什么经过那样长时间才得到发展。文章谈到，在四十年代，电子显微镜由于其分辨率大大提高而得到很大的发展，但X射线显微镜却因为没有任何改进而停滞不前。近几年，X射线显微镜得到关注大部分是因为"the development of new sources of X-ray illumination"这种采用新的照明源的X射线显微镜没得到发展是因为照明源的亮度不够。
单选题
Based on the information in the passage, what can be inferred about X-ray microscopes in the future?
【正确答案】
C
【答案解析】解析：本题考查根据已知信息进行推断的能力。由文章的最后一句话"Rather，their special properties will make possible investigations that will complement those per formed with light-and-electron based instruments"．我们得知，X射线显微镜因其特殊的性质，对光电显微镜是一个补充。其言下之意就是，x射线显微镜能提供其它种类显微镜所不能提供的信息。