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  3. TOEFL iBT Writing. In this integrated writing task, you will write a response to a question about a reading passage and a lectur

TOEFL iBT Writing. In this integrated writing task, you will write a response to a question about a reading passage and a lectur

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问题 TOEFL iBT Writing. In this integrated writing task, you will write a response to a question about a reading passage and a lecture. Your response will be scored on the quality of your writing and on how well you connect the points in the lecture with points in the reading. Typically, an effective response will have 150 to 225 words.
Reading Time - 3 minutes
For plants to grow and develop properly, they need a constant supply of chemical nutrients. The primary nutrients in soil are nitrogen, phosphorus, and potassium. These three nutrients must be replenished often because crops use them in large quantities. A chemical fertilizer with these nutrients will increase the productivity of croplands. The best fertilizer for all types of soils is a balanced 20-20-20 fertilizer containing 20 percent each of nitrogen, phosphorus, and potassium.
Nitrogen is the key element in plant growth. Soil nitrogen stimulates stem and leaf growth, resulting in lush, full plants. Plants use nitrogen to make chlorophyll molecules, so a high level of nitrogen is required for greener, healthier plants. Nitrogen dissolves in water, and plants look greener after being watered because they have absorbed nitrogen from the soil. When plants lack sufficient nitrogen, their leaves turn yellow and eventually die.
Phosphorus, which helps plants hold and transfer energy for metabolism, moves within the plant to wherever cell division is taking place. Phosphorus accelerates plant growth. It makes plants bloom faster and produce more seeds. Insufficient phosphorus causes reduced growth and seeds that will not develop. Because phosphorus is so vital to agriculture, most soils must be enriched with phosphorus-bearing minerals called phosphates, which are mined from the earth and used as chemical fertilizers.
Potassium is necessary for plant metabolism, respiration, transpiration, and cell division. When potassium-rich fertilizer is applied, plants produce strong, erect stems. Potassium is important in the plant’s manufacture of carbohydrates (sugars and starches) and oils, which contribute to the improved flavor, color, and texture of fruits, vegetables, and nuts.
Now listen to the lecture. You may take notes, and you may use your notes to help you write your response. After you hear the question, you have 20 minutes to plan and write your response. You may look at the reading passage during the writing time.
Summarize the points in the lecture, explaining how they cast doubt on points made in the reading.
Stop
Time - 20 minutes
Now listen to part of a lecture on this topic in a botany class.
Fertilizers improve crop productivity, but whenever they’re used excessively, they wash into lakes, streams, and oceans. This-is why we need to balance the benefits of fertilizers against their harmful long-term effects.
Nitrogen, a major ingredient of fertilizers, quickly washes out from the soil and into our water supply, where it’s converted to nitrates. The increasing nitrate content of our drinking water is a problem because nitrates can be poisonous to humans. Once taken into our bodies, nitrates are converted in a process that interferes with our blood’s capacity to carry oxygen, causing serious illness—and sometimes death.
Phosphorus can be equally harmful. While phosphorus promotes the growth of plants in soil, it also promotes their growth in water. If enough phosphates enter lakes and streams, they stimulate the growth of blue-green algae. Consequently, clear water becomes clouded with massive blooms of algae. When the algae die, the oxygen in the water is consumed, and this speeds up the natural aging of the lake. In just a few years, phosphates can turn a lake into a dead zone.
Another plant nutrient, potassium, is important for a plant’s production of carbohydrates. It makes vegetables look pretty and taste good, but excess potassium from fertilizers can damage the plant’s metabolism, as well as the metabolism of animals that eat the plant.
One final point I’d like to make is that different soils need nutrients in different amounts. A common mistake is using a 20-20-20 fertilizer without first doing a soil analysis to find out what the soil needs. Without doing a soil test, using a balanced fertilizer can be a waste of time and effort because it’s not likely to produce ideal conditions in every garden.
Summarize the points in the lecture, explaining how they cast doubt on points made in the reading.
选项
答案- The lecture states that when fertilizers are used excessively, they wash into lakes, streams, and oceans, with harmful effects. This casts doubt on the point in the reading that chemical nutrients must be replenished often. - The lecture states that nitrogen quickly washes into our water supply, and that nitrates in our drinking water can be poisonous. This casts doubt on the point in the reading that a high level of nitrogen is beneficial. Nitrogen helps plants but harms human health. - The lecture states that phosphorus in lakes promotes the growth of algae, which hastens the natural aging of the lake. This casts doubt on the point in the reading that phosphorus is beneficial. Phosphorus makes plants grow faster, but this is not always good. - The lecture states that excess potassium from fertilizers can damage a plant’s metabolism. This casts doubt on the point in the reading that potassium is necessary for plant metabolism. - The lecture states that different soils need nutrients in different amounts, and that a 20-20-20 fertilizer is not ideal for every garden. This contradicts the point in the reading that a 20-20-20 fertilizer is best for all types of soils.
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