Each advance in microscopic technique has provided scientists with new perspective, 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 microscopes 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 details; 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 hafted 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 available 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.,Question 35: The word "minuscule" in the first paragraph is opposite in meaning to _____.,A. circular B. dangerous C. complex D. enormous,Question 36: The word "enables" in paragraph 3 is closest in meaning to _____.,A. constitutes B. specifies C. expands D. allows,Question 37: Why did it take so long to develop the X-ray microscope?,A. Funds for research were insufficient.,B. The source of illumination was not bright enough until recently,C. Materials used to manufacture X-ray tubes were difficult to obtain.,D. X-ray microscopes were too complicated to operate.,Question 38: The word "it" in paragraph 1 refers to _____.,A. a type of microscope B. human perception C. the natural world D. light,Question 39: According to the passage, the invention of the visible-light microscope allowed,scientists to _____.,A. see viruses directly,B. develop the electron microscope later on,C. understand more about the distribution of the chemical elements,D. discover single-celled plants and animals they had never seen before,Question 40: Based on the information in the passage, what can be inferred about X-ray,microscopes in the future?,A. They will probably replace electron microscopes altogether.,B. They will eventually be much cheaper to produce than they are now.,C. They will provide information not available from other kinds of microscopes.,D. They will eventually chance the illumination range that they now use.

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{"userId":5128759,"userName":"Đặng Tú"} B A D C A C

Each advance in microscopic technique has provided scientists with new perspective, on the function of living organisms and the nature of matter itself. The invention of the visible-light microscope la...