A build-it-yourself solar still (蒸馏器) is one of the best ways to obtain drinkingwater in areas where the liquid is not readily available. Developed by twodoctors in the U.S. Department of Agriculture, it’s an excellent watercollector. Unfortunately, you must carry the necessary equipment with you,since it’s all but impossible to find natural substitutes. The only componentsrequired, 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 thewater. These pieces can be folded into a neat little pack and fastened on yourbelt.
To construct a working still, use a sharp stick or rock to dig ahole four feet across and three feet deep. Try to make the hole in a damp areato increase the water catcher’s productivity. Place your cup in thedeepest part of the hole. Then lay the tube in place so that one end rests allthe way in the cup and the rest of the line runs up — and out — the side of thehole.
Next, cover the hole with the plastic sheet, securing the edges ofthe plastic with dirt and weighting the sheet’s center down with a rock. Theplastic should now form a cone (圆锥体) with 45-degree-angled sides. The low point of the sheet must becentered directly over, and no more than three inches above, the cup.
The solar still works by creating a greenhouse under the plastic. Groundwater evaporates (蒸发) and collects on the sheet until small drops of water form, rundown the material, and fall off into the cup. When the container is full, youcan suck the refreshment out through the tube, and won’t have to break down thestill every time you need a drink.
32. What do we know about the solar stillequipment from the first paragraph?
A. It’s delicate. B. It’s expensive.
C. It’s complex. D. It’s portable.
33. What does the underlined phrase “thewater catcher” in paragraph 2 refer to?
A. The tube. B. The still.
C. The hole. D. The cup.
34. What’s the last step of constructing aworking solar still?
A. Dig a hole of a certain size.
B. Put the cup in place.
C. Weight the sheet’s center down.
D. Cover the hole with the plastic sheet.
35. When a solar still works, drops ofwater come into the cup from _____________.
A. the plastic tube
B. outside the hole
C. the open air
D. beneath the sheet