47. A study of the
art works has proved that most people--prefer to use the right hand when one
hand is needed.
A. in 93% of the
countries B.
in most historical periods
C. five thousand
years ago D.
no matter when and where
C
The world is not only hungry, but it is
also thirsty for water. This may seem strange to you, since nearly 70 percent
of the earth’s surface is covered with water. But about 97 percent of this huge
amount is sea water, or salt water. Man can only drink and use the other 3
percent-the fresh water from rivers, lakes, underground, and other sources. And
we cannot even use all of that, because some of it is in the form of icebergs
and glacier (冰川). Even worse, some of it has been
polluted.
However, as things stand today, this small
amount of fresh water is still enough for us. But our need for water is
increasing rapidly-almost day by day. Only if we take steps to deal with this
problem now can we avoid a severe worldwide water shortage later on.
We all have to
learn how to stop wasting our valuable water. One of the first steps is to
develop ways of reusing it.
Today in most
large cities, water is used only once and then sent out into a sewer system (下水道). From there it returns to the sea or runs into
underground storage tanks. But it’s possible to pipe used water to a purifying
plant. There it can be treated with chemicals so that it can be used again,
just as if it were fresh from a spring.
But even if every large city purified and
reused its water, we still would not have enough. All we’d have to do make use
of the vast reserves of sea water in the world is to remove the salt.
If we take these steps we’ll be in no
danger of drying up.
