DOCX《绝密启封前 试卷类型A》

s all but impossible to find natural substitutes. The only components required, though, are a 5'

5'

sheet of clear or slightly milky plastic, six feet of plastic 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 rock to dig a hole four feet across and three feet deep. Try to make the hole in a damp area to increase the water catcher'

s productivity. Place your cup in the deepest part of the hole. Then lay the tube in place so that one end rests all the way in the cup and the rest of the line runs up ― and out ― the side of the hole. Next, cover the hole with the plastic sheet, securing the edges of the plastic with dirt and weighting the sheet'

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 sheet must be centered ........