Once you find water, a major issue remains: Is it pure? Is it drinkable? And if not, how to make it drinkable?
You can make a water filler（过滤器）from a cone of birch bark（桦树皮）. This cone is then filled with layers of sand, charcoal（木炭）, grasses, and other materials. Grasses and sand help to trap suspended particles（悬浮颗粒）. Charcoal helps to remove chemical impurities, but not bacteria. You may have to pass the water through the filter more than once, depending on the site of the filter and what it's made of. Generally speaking, the bigger the filler, and the more layers you have in it, the better.
The birch bark cone will need to have a fairy small hole in the bottom. The cone will have to be tied with cordage to keep it from opening up. Put a few stones in the very bottom, to help hold your filtering materials in place. Then pour in lavers of charcoal, grasses, sand, and possibly other materials that you feel will help to filter out suspended particles and perhaps even bacteria.
Once you have constructed the filter, simply pour impure water through the filer, catching it in another container at the bottom.
This is basically the "well" method of obtaining water. Dig a hole about 2 4 feet from a water source, such as a river. Allow the hole to fill with water. The water in the hole will likely be reasonably pure.
【小题1】How do we get purer water?| A．Bigger filter and less layers. | B．Smaller filler and more layers. |
| C．Larger filter and more layers. | D．Smaller filter and less lavers. |
| A．Killing bacteria. | B．Removing chemicals. |
| C．Blocking water. | D．Keeping the materials balanced. |
A． | B． | C． | D． |
| A．absorbing water | B．cleaning water | C．finding water | D．boiling water |
