VOA慢速英语:Nations Work Toward Aim of Zero Malaria Deaths by 2015

例句：The disease ranges widely in severity.
       这种病的严重程度可以很不同。

      The drug can reduce the frequency and severity of attacks.
      这种药能降低发病次数和严重程度。

2.estimate vt.vi.估计; 评价, 评估

例句：The gardener estimated that it would take him four hours to weed the garden.
      园丁估计他给花园除草需要四个小时。

3.resistance n.抵抗, 反抗, 抵抗能力

例句：The defenders put up a strong resistance.
      守军顽强抵抗。

4.expel vt.驱逐, 赶走, 放逐,驱逐出境

例句：They expelled a foreign spy from their country.
      他们把一个外国间谍驱逐出境。

5.observe vt.vi.观察; 研究

例句：He observes carefully but says little.
      他总是仔细观察, 很少说话。

6.protective adj.保护的, 防护的

例句：We feel safe with a protective device in the house.
      我们因为家里有了防护装置而感到安全。

7.independently adv.独立地,自立地;无关地

例句：The enquiry must be independently conducted.
      这次调查必须独立进行。