4.
A buld-it-yourself solar still(蒸馏器) is one of the best ways toobtain
drinking water in areas where the liquid is not readily available.Developed by
two doctors in the U.S. Department of Agriculture, it’s anexcellent water
collector. Unfortunately, you must carry the necessaryequipment with you, since
it’s all but impossible to find natural substitutes.The only components
required, though, are a
sheet of clear orslightly milky plastic, six feet of plastic tube, and a
container— perhaps justa drinking cup — to catch the water. These pieces can be
folded into a neatlittle pack and fastened on your belt.
To construct a working still, use a sharpstick or rock to dig a hole four feet across and three feet deep. Try to makethe hole in a damp area to increase the water catcher’s productivity. Place your cup in the deepestpart of the hole. Then lay the tube in place so that one end rests all the wayin 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 centerdown 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 directly over, and no more thanthree inches above, the cup.
The solar still works by creating agreenhouse under the plastic. Ground water evaporates (蒸发) and collects on the sheet untilsmall drops of water form, run down the material and fall off into the cup.When the container is full, you can suck the refreshment out through the tube,and won’t have to break down the still every time you need a drink.
32.What do we knowabout the solar still equipment from the first paragraph?
A.It’sdelicate. B.It’sexpensive.
C.It’scomplex. D.It’s portable
33.What does theunderlined phrase “the water catcher” in paragraph 2 refer to?
A.The tube B.The still
C.The hole D.The cup
34.What’s the laststep of constructing a working solar still?
A.Dig a hole of acertain size
B.Putthe cup in place
C.Weight thesheet’s center down
D.Cover the hole with the plastic sheet
35.When a solarstill works, drops of water come into the cup form .
A.the plastictube B.outside thehole
C.the openair D.beneaththe sheet
参考答案
DBCD
