单选题Directions: These are 15 blanks in the following passage. Read the
passage through.Then, go back and choose the most suitable of the words or
phrases marked A, B, C and D for each blank in the passage. Mark the
corresponding letter of the word or phrase you have chosen with a single bar
across the square brackets on your Machine-scoring Answer
Sheet. Acid rain leads to fish
mortality. Many species of fish cannot survive in aquatic environments there the
pH is below 5.0. If the water is too acid, the gill systems of many kinds of
fish can be damaged.{{U}} {{U}} 1 {{/U}} {{/U}},
the acid alters the blood chemistry of all fish. As a result,the fish population
in an acidic environment decreases{{U}} {{U}} 2 {{/U}}
{{/U}}becomes extinct. Approximately 20 percent of the lakes in Scandinavia
are without fish. Moreover, in Nova Scotia the{{U}} {{U}} 3
{{/U}} {{/U}}salmon industry may be threatened by the decrease of
salmon in rivers and streams. The impact is also{{U}} {{U}}
4 {{/U}} {{/U}}in the waters of Ontario and Quebec, where fish
populations are{{U}} {{U}} 5 {{/U}} {{/U}}the
decline. What potential remedies exist for the acid
rain{{U}} {{U}} 6 {{/U}} {{/U}}? The experts
disagree. Some say new environmental laws should be{{U}} {{U}}
7 {{/U}} {{/U}}to control the emission of pollutants in the
atmosphere. Some say that if we had known how serious acid rain was, we would
have planned{{U}} {{U}} 8 {{/U}} {{/U}}to prevent
it.{{U}} {{U}} 9 {{/U}} {{/U}}, all agree that if
the consumption of fossil fuel were reduced, we would have less of a problem.
Another{{U}} {{U}} 10 {{/U}} {{/U}}is that special
scrubbers could be installed in smokestacks to remove a good{{U}}
{{U}} 11 {{/U}} {{/U}}of the pollutants before they get into
the atmosphere. Other ideas even include breeding more{{U}} {{U}}
12 {{/U}} {{/U}}fish. And research suggests that spreading lime
into lakes may be effective in{{U}} {{U}} 13 {{/U}}
{{/U}}acidity. In conclusion, it is clear that if we truly want to reduce
the impact of acid rain, a{{U}} {{U}} 14 {{/U}}
{{/U}}of remedies and international cooperation must be explored. It is a sad fact
that acid rain probably could have been avoided if we{{U}} {{U}}
15 {{/U}} {{/U}}what we know now.