补充练习 2017 年全国高考 I 卷 D 篇 D A build-it-yourself solar still( 蒸馏器 ) is one of the best ways to obtain drinking water inareas where the liquid is not readily available. Developed by two doctors inthe U.S. Department of Agriculture, it’s an excellent water collector.Unfortunately, you must carry the necessary equipment with you, since it’s allbut impossible to find natural substitutes. The only components required,though, are a 5′×5′ sheet of clear or slightly milky plastic, six feet ofplastic tube, and a container—perhaps just a drinking cup—to catch the water.These pieces can be folded into a neat little pack and fastened on your belt. To construct a working still, use a sharp stick or rockto dig a hole four feet across and three feet deep. Try to make the hole in adamp area to increase the water catcher ’s productivity. Place your cupin the deepest part of the hole. Then lay the tube in place so that one endrests all the way I n the cup and the rest of the line runs up—and out—the sideof the hole. Next, cover the hole with theplastic sheet, securing the edges of the plastic with dirt and weighting thesheet’s center down with a rock. The plastic should now form a cone (圆锥体) with 45-degree-angled sides. The low point of the sheetmust be centered directly over, and no more than three inches above, the cup. The solar still works bycreating a greenhouse under the plastic. Ground water evaporates (蒸发) and collects on the sheet until small drops of waterform, run down the material, and fall off into the cup. When the container isfull, you can suck the refreshment out through the tube, and won’t have tobreak down the still every time you need a drink. 33. What does the underlinedphrase “the water catcher” in paragraph 2 refer to? A.The tube. B. The still. C. The hole. D. The cup.