填空题Questions 24-26 Complete the
sentences below. Use NO MORE THAN TWO WORDS from the reading
passage for each answer. Certain birds have a bigger singing
{{U}} {{U}} 11 {{/U}} {{/U}}than they actually need.
Female birds might start to choose mates who are able to avoid {{U}}
{{U}} 12 {{/U}} {{/U}} It is possible that in
future bird species might {{U}} {{U}} 13 {{/U}} {{/U}}in
response to differing noise levels.