簡單的一篇。
Scientific consensus is that humans first began to have a warming effect on Earth’s climate within the past century, after coal-burning factories, power plants, and motor vehicles began releasing carbon dioxide (CO2) and other greenhouse gases in significant quantities into the air. However, evidence suggests that human agricultural activities may have had such an effect much earlier: concentrations of CO2 started rising about 8000 years ago, even though natural trends indicate they should have been dropping; methane levels rose similarly about 3,000 years later.Without these rises, however, current temperatures in northern parts of North America and Europe would be cooler by three to four degrees Celsius-enough to inhibit agriculture-and an ice age would probably have begun several thousand years ago in northeastern Canada.
1. Which of the following best describes the function of the highlighted sentence?
A. It undermines the assumption that human activity has had a significant impact on Earth’s climate
B. It supports the assumption that Earth’s temperatures have risen appreciably over the past 100 years
C. It questions the assumption that greenhouse gases have had a warming effect on Earth's climate
D. It challenges the assumption that human activity began to affect Earth’s climate after the advent of industrialization
E. It supports the assumption that greenhouse gases are a direct by-product of industrial activities
答案：D
2. The author mentions “natural trends” most likely in order to
A. propose a possible explanation for why current temperatures in North America and Europe are not as low as they might otherwise be
B. explain why levels of methane in Earth's atmosphere began to rise approximately 5,000 years ago
C. suggest that Earth’s climate would have become even warmer without the advent of human agricultural activities
D. identify factors that may have contributed to the rise of greenhouse gases in Earth’s atmosphere approximately 8,000 years ago and again some 3,000 years later
E. support the claim that human activity may have played a role in the rise in CO2 and methane levels in the atmosphere thousands of years ago
答案：E
解析見下。
Scientific consensus is that humans first began to have a warming effect on Earth’s climate within the past century, after coal-burning factories, power plants, and motor vehicles began releasing carbon dioxide (CO2) and other greenhouse gases in significant quantities into the air.
第1句：科學界的共識是，人類第一次開始對地球氣候產生變暖的影響是在過去的一個世紀裡，在燃煤工廠，發電廠和機動車輛開始大量釋放二氧化碳（CO2）和其他溫室氣體到空氣中之後。
【燃煤工廠，發電廠和機動車輛】是工業時代的標誌。
此句蘊含著因果關係：因為人類在過去的一個世紀中——也就是從工業時代以來——開始大量釋放二氧化碳（CO2）和其他溫室氣體到空氣中，所以從此開始對地球氣候產生變暖的影響。
同時意味著，工業時代之前的人類對氣候沒什麼影響。
注意，上述是個觀點，不是已經得到證實的客觀事實。
However, evidence suggests that human agricultural activities may have had such an effect much earlier: concentrations of CO2 started rising about 8000 years ago, even thoughnatural trends indicate they should have been dropping; methane levels rose similarly about 3,000 years later.
第2句：然而，有證據表明，人類農業活動可能早已有這樣的效果：儘管自然趨勢表明二氧化碳濃度應該已經下降，但二氧化碳濃度在大約8000年前開始上升；大約3000年後，甲烷含量同樣也出現上升。
在人類進入工業時代之前，處於農業時代。
有證據和第一句的觀點形成了矛盾。
有證據表明，人類的農業活動早已對氣候產生影響——也就是，人類在農業時代的時候，農業活動就已經對氣候產生了影響。
前提：自然趨勢表明二氧化碳濃度應該已經下降。
現實狀況：二氧化碳濃度在大約8000年前開始上升；距今8000年前的大約3000年後——也就是大約5000年前，甲烷含量同樣也出現上升。
大約8000年前到工業時代之前的時間，屬於農業時代。
這說明：人類對氣候的影響也許並不是到了工業時代才開始；農業時代也許就開始了。
Without these rises, however, current temperatures in northern parts of North America and Europe would be cooler by three to four degrees Celsius-enough to inhibit agriculture-and an ice age would probably have begun several thousand years ago in northeastern Canada.
第3句：但凡沒有這些上升，北美和歐洲北部地區目前的氣溫將會降低3到4攝氏度，足以抑制農業生產，並且加拿大東北部可能已經在數千年前就開始了冰河期。
這些——指第二句的二氧化碳、甲烷這兩種溫室氣體。如果它們沒有上升的話，當前的北美和歐洲北部地區會相當冷。冷到什麼程度？冷到無法農業生產的程度，甚至會冷到讓加拿大東北部處於冰河期。
句子內涵：表現出了作者沒直接說出的看法——人類的農業活動（從至少8千年前就開始了）對氣候有影響，並且影響還相當大。
文章小結：文章和題目都不難，但是需要讀者具備一點基本常識：人類從農業時代進入工業時代；工業時代才有【燃煤工廠，發電廠和機動車輛】。
1. Which of the following best describes the function of the highlighted sentence?
1.以下哪項最能描述高亮句子的功能？
However, evidence suggests that human agricultural activities may have had such an effect much earlier
這其實就是作者心裡的想法，與老觀點不同——挑戰了老觀點。所以選D。
D. It challenges the assumption that human activity began to affect Earth’s climate after the advent of industrialization
D.它挑戰了人類活動在工業化出現後開始影響地球氣候的假設
【人類活動在工業化出現後開始影響地球氣候】就是老觀點。
看錯誤選項。
A. It undermines the assumption that human activity has had a significant impact on Earth’s climate
A.它破壞了人類活動對地球氣候產生重大影響的假設
作者從未否認過人類活動對地球氣候產生了重大影響。作者有異議的是，是從什麼時候開始產生重大影響的。
B. It supports the assumption that Earth’s temperatures have risen appreciably over the past 100 years
B.它支持了過去100年來地球溫度明顯上升的假設
首先，文章也沒說過去100年來地球溫度【明顯】上升。其次，這句話是在質疑人類活動【對溫度的影響】開始的時間，不是在支持哪個假設。
C. It questions the assumption that greenhouse gases have had a warming effect on Earth's climate
C.它質疑溫室氣體對地球氣候產生變暖的假設
作者從未否認過溫室氣體造成地球氣候變暖。
第二題解析略。需要解析請留言。
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