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Tham khảo tài liệu 'how to prepare for the toefl part 60', ngoại ngữ, toefl - ielts - toeic phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | MODEL TEST 5 COMPUTER-ASSISTED TOEFL 593 Wood Wire mesh shavings 43. 44. Nutrient solution Air entry Audio What is hydroponics Answer A . hydroponics is the science of growing plants without soil. Choice B refers to the nutrients that are used in the solution in order to grow the plants not to a definition of hydroponics. Choices C and D are not mentioned and may not be concluded from information in the lecture. Audio Why does the professor suggest that the students refer to the lab workbooks Answer C You can refer to your lab workbook for the list of substances and the proportions needed for proper plant growth. Choice A is not correct because the professor shows the diagram. Choice D is not correct because the hydroponics tank is already built and displayed in class. Choice B is not mentioned and may not be concluded from information in the lecture. pump For now let s look at the diagram that we worked on last time when we began our hydroponics experiment. Your drawing should look more or less like this one. As you know for plants grown in soil the roots not only absorb water and nutrients but also serve to anchor the plant. That is why the roots of our hydroponic plants are not placed directly in the water and nutrient solution. We used wood chips held in place by wire mesh to anchor the plants and allow us to suspend the roots in the tank below that contains the water and nutrient solution. Because oxygen is also taken in by the roots we had to attach an air pump to mix oxygen into the solution. And you can see the way that the pump was attached to the tank. During our break this morning I d like you to come over to the hydroponics area and examine the experiment close up. I d also like you to take a closer look at this specimen of nutrient solution. What do you notice about this What conclusions can you draw Now get ready to answer the questions 594 EXPLANATORY ANSWERS AND AUDIO SCRIPTS Audio 45. According to the speaker why are roots important to plants .
