根据网考网考试中心的统计分析，以下试题在2019/10/10日考博习题练习中，答错率较高，为：60%
【单选题】
{{B}}Directions:{{/B}} There are 5 reading passages in this part.Each passage is followed by some questions or unfinished statements. For each of them there are four choices markedA,B,C, andD、You should decide on the best choice and mark your answer on theANSWER SHEET by blackening the corresponding letter in the brackets.
Dr. Martin Jacobson of Silver Spring, MD、, assigned patent rights to the U. S. Government as represented by the Secretary ofAgriculture. The chemical can be used to detect gypsy moth infestations, as well as to control the insects.
The gypsy moth does serious damage to forest and shade trees in NewEngland and eastern New York State. The caterpillars, or larvae, of gypsy moths eat the leaves of trees, often causing death by a single attack. Losses of hardwood trees have been estimated at tens of millions of dollars from a 20-year study.
Gypsy moths were prevented from spreading to other U. S. forest areas by using the natural attractant of the female to detect infestations, then spraying with chemicals such asDDT to kill the insects.
Since the lure could previously be obtained only by clipping the last two abdominal segments of the virgin female moth, extracting the segments with benzene and then processing to stabilize the chemical, the procedure was expensive.Another difficulty was that, as the gypsy moth population declined, it became increasingly hard to obtain the females needed for lure production.
Dr. Jacobson overcame both these difficulties by discovering a synthetic method for making the female’s attractant chemical. The chemical is known as 12-acetoxy-l-hydroxycis-9- octadecene. It is so potent that the fraction of a drop produced by the female is 200,000 times more than the amount needed to catch a mate. The synthetic chemical is also very powerful--it works in amounts about equivalent to one drop in a box car.
The flightless female gypsy moth mates only once a year and, as soon as she does, an enzyme switches off production of the sex attractant. The winged male, however, call mate several times and it is because of this that the chemical is being used for pest control.
By using a mixture of attractant andDDT in traps lined with a sticky substance, enough males can be caught to reduce the gypsy moth population substantially.
B．only the female moth
C、a substitute female attractant
D．caterpillars
网考网参考答案：D，答错率：60%
网考网试题解析：
舞毒蛾给新英格兰和纽约的树木造成的危害是由毛虫造成的。根据第三段第二句，舞毒蛾的毛虫或幼虫吃树叶，往往通过一次袭击就导致树木死亡。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>
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