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  3. Sugar cane was once a wild grass that grew in New Guinea and was used by local people for roofing their houses and fencing their

Sugar cane was once a wild grass that grew in New Guinea and was used by local people for roofing their houses and fencing their

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问题     Sugar cane was once a wild grass that grew in New Guinea and was used by local people for roofing their houses and fencing their gardens. Gradually a different variety evolved which contained sucrose(蔗糖)and was chewed on for its sweet taste. Over time, sugar cane became a highly valuable commercial plant, grown throughout the world. 【B1】______
    Sugar became a vital ingredient in all kinds of things, from confectionery(糖果点心)to medicine , and, as the demand for sugar grew, the industry became larger and more profitable.【B2】______Many crops withered(枯萎)and died, despite growers, attempts to save them, and there were fears that the health of the plant would continue to deteriorate.
    In the 1960s, scientists working in Barbados looked for ways to make the commercial species stronger and more able to resist disease. They experimented with breeding programmes, mixing genes from the wild species of sugar cane, which tends to be tougher, with genes from the more delicate, commercial type.【B3】______This sugar cane is not yet ready to be sold commercially, but when this happens, it is expected to be incredibly profitable for the industry.
    【B4】______Brazil, which produces one quarter of the world’ s sugar, has coordinated an international project under Professor Paulo Arrudo of the Universidade Estaudual de Campinas in Sao Paulo. Teams of experts have worked with him to discover more about which parts of the genetic structure of the plant are important for the production of sugar and its overall health.
    Despite all the research, however, we still do not fully understand how the genes function in sugar cane.【B5】______This gene is particularly exciting because it makes the plant resistant to rust, a disease which probably originated in India, but is now capable of infecting sugar cane across the world. Scientists believe they will eventually be able to grow a plant which cannot be destroyed by rust.
[A]Unfortunately, however, the plant started to become weaker and more prone to disease.
[B]Sugar cane was now much vigorous and the supply of sugar is therefore more guaranteed.
[C]One major gene has been identified by Dr Angelique D’ Hont and her team in Montpe-lier, France.
[D]The majority of the world’ s sugar now comes from this particular commercial species.
[E]Since the 1960s, scientists have been analysing the mysteries of the sugar cane’ s genetic code.
[F]The sugar cane’ s genetic code has been found by a farmer in 1950.
[G]Eventually, a commercial plant was developed which was 5 percent sweeter than before, but also much stronger and less likely to die from disease.
【B2】
选项
答案A
解析 上一句讲到糖是所有东西的一个重要成分，因此对糖的需求在增长，下一句说到“尽管种植者试图拯救它们，仍有许多作物枯萎死亡”。由此可知，空格处与前面形成转折关系，故选A。
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