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- D
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- F
Read the following passage. Then try to make notes of the key facts.
DDT is a human-manufactured chemical once used to control the spread of unwanted insects. It was used during World War II to kill mosquitoes carrying dangerous human diseases, and afterwards to get rid of agricultural pests. Over time, however, scientists discovered that DDT did much more harm than good.
DDT, although designed to protect humans and plants from disease-carrying insects, is itself a hazard to the environment. It accumulates in the soil and in small bodies of water and is then ingested by animals such as fish and birds. Because DDT is not easily digested, it gets stored in the body and builds up over time. Too much DDT can poison and even kill wildlife. It is, for example, a major factor in the decline of the bald eagle.
DDT also endangers the health of humans who consume produce sprayed with DDT. Studies have shown that exposure to DDT increases the risk of diabetes, birth defects, and various forms of cancer. The effects of DDT consumption were found to be so severe that the United States eventually banned the chemical
Finally, DDT has failed to effectively combat disease-carrying mosquitoes, and thus diseases like malaria continue to spread. Not long after DDT was first introduced on the market, mosquitoes began developing a resistance to the chemical. It was not long before mosquitoes could once again easily transmit deadly diseases.
pest – a small animal or insect that annoys you
hazard – something that is dangerous
accumulate – to become larger over time
Ingest – to eat or drink something
produce – fruit and vegetables
resistance – the ability not to get sick from something
combat – to fight or oppose something
transmit – to send something from one place to another
Reading:
Now look at the note diagram and fill in the missing information from your notes.
Improve your notes if necessary. Try to summarize the text using your notes.
Reading:
Below is important information from the reading passage above. After each sentence there are two possible paraphrases of it. Choose the best paraphrase for each sentence. Explain the reasons for your choice.
Reading:
Predict how the listening passage may contrast with the reading.
notorious – well-known for something bad
Insecticide – a chemical used to kill insects
toxic – poisonous
impair – to make something worse or less effective
escalate – to increase in intensity
inconclusive – not certain
devastating – very damaging
intensive – involving a lot of energy or a lot of parts
Now listen to a lecture related to the topic in A. Make notes while listening.
Listening
Fill in the blanks of the note diagram below with keywords or key phrases used in the lecture.
Summarize the contents of the lecture expanding the diagram above and using your notes.
M: So, perhaps the most well-known example of an insecticide is DDT. Now, DDT is notorious for being an extremely dangerous chemical. It's been criticized for its toxic effects on the environment, on humans, and for its inability to completely wipe out disease. But let me remind you that, despite its downsides, DDT wasn't nearly as bad as we've been made to believe. In fact, it had several benefits.
First of all, DDT can, in some cases, benefit plants and animals. Yes, DDT, when consumed in extremely large quantities, will impair, or even kill, an animal. But in smaller quantities… which is how it was most often found to be in the environment... it mostly just kills insects, which can spread diseases from plant to plant or animal to animal. Insect-born diseases have been known to wipe out huge populations of species. And so, by preventing insect populations from escalating, DDT prevents certain animal and plant populations from shrinking.
DDT can also benefit human health. Again, DDT can be toxic if you ingest it in large quantities, but even the World Health Organization considers it only "moderately hazardous." Which means that in smaller quantities, DDT doesn't really do much at all if you happen to ingest it. Sure, there are studies that show a correlation between DDT and things like cancer or reproductive disease, but many of these studies are inconclusive. What DDT does do, though, is kill the insects that spread deadly human diseases, like malaria or typhus. Such diseases have far more devastating effects on human health than DDT ever had. So by reducing their spread, DDT in fact improves public health.
Lastly, DDT has effectively combated diseases, particularly malaria, in the past. Although some mosquitoes have now developed a resistance to DDT, there are many cases in which it successfully wiped out the disease. Sri Lanka, for example, had 1.5 million cases of malaria between 1934 and 1955; 80,000 people died. The year after the country completed an intensive anti-mosquito program using DDT, only seventeen cases were reported. Since then, millions of lives have been saved because of the widespread use of DDT.
Listening:
Choose the sentences that best combine the main idea and key points from the reading passage and the lecture. Explain the reasons for your choice.
Below are four incomplete paraphrases of key information from the reading passage and the lecture. Choose the most suitable words or phrases from the options suggested. These words and phrases are synonyms or are similar in meaning to the actual words used in the reading passage and lecture.
Read the following sentences taken from the reading and the lecture. Create new sentences by combining the ideas in each pair of sentences.
- 1. Diseases that start with insects can kill entire populations, although in the case of the bald eagle, DDT was mostly responsible for its population decline.
- 2. The United States eventually banned DDT because it was too dangerous, though some argue that diseases spread by mosquitoes are worse.
