【正确答案】The Deterioration of the Environment
Throughout history/ Through the ages, man/ mankind/ humanity has been consistently changing nature (has changed his physical environment) in order to improve his way of life. With the tools/instruments of technology he has altered many physical features of the earth. He has transformed woodlands/forests and prairies into farms and made lakes and reservoirs out of rivers for irrigation purposes or hydroelectric power (for irrigation and power generation). Man has also modified/ altered the face/ appearance of the earth by draining marshes, cutting through mountains and building roads and railways. However, man's changes to the physical environment have not always had beneficial results. Today, pollution of the air and water is (foul air and filthy water constitute) an increasing danger to the health of the planet. Each day thousands of tons of gases come out of the exhausts of motor vehicles. Smoke from factories pollutes the air of industrialized areas and the surrounding areas of the countryside. The pollution of water is equally harmful. The whole ecological balance of the sea is being changed, and industrial wastes have already made many rivers lifeless. Now environmental protection is more pressing than ever before. As we know, massive destruction of the environment has brought about negative effects, and even posed a threat to man's (very) existence (and even human life is in danger/jeopardy) (and even humankind is threatened with extinction). Indifference to these problems will mean committing suicide. (Ignoring those dangers means suicide/ would be suicidal.
·