下边就跟随我一起掌握英语四级学习英语听力分享，期待对大伙儿的学习培训有一定的帮助。
一、听力训练
1.
A. 25 percent.
B. 9 percent.
C. 11 percent.
D. 24 percent.
2.
A. Climate change.
B. Air pollution.
C. Clean-water policies established in recent years.
D. Widespread of insecticide.
二、英语听力文字
Researchers say the world has lost more than one fourth of its land-based insects over the past 30 years. The researchers noted the loss of such bugs suggests a more complex problem than earlier research has shown. Ants, bees, butterflies and other land-based bugs have been suffering population drops of about nine percent every 10 years or so. But freshwater insects, such as dragonflies and mosquitoes, have been growing in number over the years. The researchers found that different areas have experienced different rates of insect decline. Overall, bugs are disappearing at a rate of just under one percent a year, with the strongest declines reported in the United States and Germany. Ongoing decline on land at this rate will be extremely damaging for ecological systems and for humans. The researchers also studied insects that spend at least part of their lives in freshwater. These bugs were found to have experienced a population increase of about 11 percent every 10 years. Freshwater covers only about 2.5 percent of the Earth's surface, so the majority of insects live on land. The number of insects on average has declined in the air, in the grass and soil, but not in trees or underground, the researchers found. Some estimates show that land-based insects would face a population drop of 24 percent over the next 30 years. Freshwater bugs would experience a 38 percent increase over the same period. The researchers said clean-water policies established in recent years were responsible for the increase in freshwater bugs.
Question 1: According to the news report, how much will the population of land-based insects drop over the next 30 years?
Question 2: According to the news report, what is responsible for the increase in freshwater bugs?

三、关键语汇
1. ongoing: continuing to exist or develop, or happening at the present moment 不断存有的；持续发展趋势的；再次开展的；进行中的