雅思阅读练习题(6)
本文为大家收集整理了雅思阅读练习题。雅思阅读备考中，同学们需要选择一些难度恰当的练习题来练习并检测自己的复习效果。
You should spend about 20 minutes on questions 14-26, which are based on Reading Passage 2 below.
Question 14
Choose the most suitable title for Reading passage 2 from the list below. Write your answer in box 14 on your answer sheet.
A Old Remedies Still Work Today.
B The Forest Pharmacy.
C Miracle Cure From Nature.
D A Modern Cure For An Ancient Killer
A
The search for cures to treat common diseases is not new, nor is it unusual to find the cures for such diseases in tree bark. Aspirin for headaches and quinine for the treatment of malaria are both examples
of modern medicines which have been derived from tree bark. But the latest additions to this list may be the most significant yet, according to the findings of research into the medicinal benefits of the bark of the African Bush Willow. At an international conference, Dr Scott Remick of the USA claimed that combretastin, a product of this bark, has proved up to 85% effective in combating cancer, and may, in combination with chemotherapy, finally provide a way to destroy many types of tumour.
B
The African Bush Willow, which grows in South Africa, has been recognised as a medicinal plant by local tribespeople for many years. In the past, its roots were used as purgatives and its gum was used to treat sores and ulcers. Common along river banks in southern Africa, this plant (scientific name, Combretum caffrum) has proved both hardy and prolific, It is one of the world's fastest-growing trees and can grow one metre in height annually to a maximum of fourteen metres. To sustain this level of growth normally requires warmth, rich soil and abundant water. but even when these are in short supply, the African Bush Willow can survive. It is resistant to severe drought and even sustained periods of frost, and temperatures well below zero do not damage the tree.
C
Combretastin, the active ingredient in the bark, was originally isolated form the stems and branches in the 1970a by South African researcher, Dr Gordon Cragg. A massive seventy-seven kilogrammes of material was needed from the tree to produce just a few milligrams of the active ingredient. However, scientists have now been able to produce the drug synthetically. This type of manufacturing has meant that the drug can now be mass-produced and used much more widely in the treatment of cancer. Most cancers are caused by tumours, which create their own network of capillaries to supply the blood they need in order to grow. The effect of combretastin is to reduce the tumour's ability to create these capillaries and thereby starve the tumour to death.
D
Combretastin appears to work very quickly, often reducing the blood flow to a tumour within four to six hours after its first application.
A feature in its favour is that combretastin does not appear to affect the blood supplies to other healthy organs. But, used in isolation, a small number of cancerous cells which appear able to live off normal blood supplies, appear to remain unaffected by combretastin, and radiation therapy is required to destroy these cells and remove the threat of cancer altogether.
