All correct in 14 mins 45 seconds, including 5 mins 30 seconds to read.
Para 1- 2 developments that led to current major research effort on nitrogen fixation- rise in price of nitrogen fertilizer and growth in genetic engineering
Para 2- Nitrogen fixation; the irony; symbiotic relationship between leguminous plants and Rhizobium
Para 3- Unfortunately most of major food crops cannot do symbiosis with R; an additional, formidable challenge to plant geneticists
1. The primary purpose of the passage is to
(D) explain the reasons for and the objectives of current research on nitrogen-fixing symbioses- Correct, the two reasons are mentioned in first para and the objective is listed in third para.
2. According to the passage, there is currently no strain of Rhizobium that can enter into a symbiosis with
(C) maize
The leguminous plants - among them crop plants such as soybeans, peas, alfalfa, and clover - have solved the nitrogen supply problem by entering into a symbiotic relationship with the bacterial genus Rhizobium
3. The passage implies that which of the following is true of the bacterial genus Rhizobium?
(E) Rhizobium bacteria produce some ammonia for their own purposes.- Correct
The host plant supplies the bacteria with food and protected habitat and receives surplus ammonia in exchange.
4. It can be inferred from the passage that which of the following was the most influential factor in bringing about intensified research on nitrogen fixation?
(B) The persistent upward surge in natural gas prices
The one development has been the rapid, sustained increase in the price of nitrogen fertilizer.
Fertilizer prices, largely tied to the price of natural gas, huge amounts of which go into the manufacture of fertilizer, will continue to represent an enormous and escalating economic burden on modern agriculture, spurring the search for alternatives to synthetic fertilizers.
5. Which of the following situations is most closely analogous to the
situation described by the author as one of nature's great ironies?
(C) That of shipwrecked sailors at sea in a lifeboat, with one flask of drinking water to share among them - Correct; I am reminded of a line from a poem 'water water everywhere not a drop to drink'
It is one of nature's great ironies that the availability of nitrogen in the soil frequently sets an upper limit on plant growth even though the plants' leave are bathed in a sea of nitrogen gas.
6. According to the passage, the ultimate goal of the current research on nitrogen fixation is to develop
(A) strains of Rhizobium that can enter into symbioses with existing varieties of wheat,rice, and other nonlegumes - incorrect, the bacteria used for fixation need not be Rhizobium
(D) varieties of wheat, rice, and other nonlegumes that maintain an adequate symbiotic relationship with nitrogen-fixing bacteria and produce high yields - Correct, the scientist need to work on varieties of wheat, rice and other nonlegumes and work on enhancing fixation within the existing symbioses
This poses an additional, formidable challenge to plant geneticists: they must work on enhancing fixation within the existing symbioses. Unless they succeed, the yield gains of the Green Revolution will be largely lost even if the genes in legumes that equip those plants to enter into a symbiosis with nitrogen fixers are identified and isolated, and even if the transfer of those gene complexes, once they are found, becomes possible.
7. The author regards the research program under discussion as
(B) necessary and ambitious but vulnerable to failure - Correct
The overall task looks forbidding, but the stakes are too high not to undertake it.
8. Most nearly parallel, in its fundamental approach, to the research program described in the passage would be a program designed to
(D) change the genetic makeup of food plants that cannot live in water with high salinity, using genes from plants adapted to saltwater - Correct
plants that live water with high salinity are analogous to leguminous plants with a symbiotic relationship with the bacterial genus Rhizobium
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