Efforts to control Spartina outside its natural environment have included burning, flooding, shading plants with black canvas or plastic, smothering the plants with dredged materials or clay, applying herbicide, and mowing repeatedly. Little success has been reported in New Zealand and England; Washington State’s management program has tried many of these methods and is presently using the herbicide glyphosphate to control its spread. Work has begun to determine the feasibility of using insects as biological controls, but effective biological controls are considered years away. Even with a massive effort, it is doubtful that complete eradication of Spartina from nonnative habitats is possible, for it has become an integral part of these shorelines and estuaries during the last 100 to 200 years. (TPO22-Spartina)
According to the paragraph, each of the following methods has been used in attempts to control Spartina EXCEPT
A: flooding plants
B: cutting plants down repeatedly
C: applying herbicides
D: introducing predatory insects
本题选对的关键点在于题干的时态，has been used应该翻译为已经被使用，第4个选项虽然原文提及，但并非已经被使用的控制方法。
The weather, in its many forms, is the main agent of erosion. Rain washes away loose soil and penetrates cracks in the rocks. Carbon dioxide in the air reacts with the rainwater, forming a weak acid (carbonic acid) that may chemically attack the rocks. The rain seeps underground and the water may reappear later as springs. These springs are the sources of streams and rivers, which cut through the rocks and carry away debris from the mountains to the lowlands.
Why does the author mention Carbon dioxide in the passage?
A: To explain the origin of a chemical that can erode rocks
B: To contrast carbon dioxide with carbonic acid
C: To give an example of how rainwater penetrates soil
D: To argue for the desirability of preventing erosion
本题正确答案为第1个选项。容易误选的是第3个选项。请观察：penetrates这一动作在原文作用的对象是谁？对，是cracks in the rocks而非soil，对于soil的动作应该是washes away.本质意思并不相同。打个比方，“买书，看猩猩“，改成“看书，买猩猩“，完全不是一个意思。