单选题
In the early days of sea travel, seamen on long voyages lived exclusively on salted meat and biscuits. Many of them died of scurvy (坏血病), a disease of the blood which causes swollen gums, livid white spots on the flesh and general exhaustion. On one occasion, in 1535, an English ship arrived in Newfoundland with its crew desperately iii. The men"s lives were saved by Iroquois Indians who gave them vegetable leaves to eat. Gradually it came to be realized that scurvy was caused by some lack in the sailors" diet and Captain Cook, on his long voyages of discovery to Australia and New Zealand, established the fact that scurvy could be warded off by the provision of fresh fruit for the sailors.
Nowadays it is understood that a diet which contains nothing harmful may yet result in serious disease if certain important elements are missing. These elements are called "vitamins". Quite a number of such substances are known and they are given letters to identify them, A, B, C, D, and so on. Different diseases are associated with deficiencies of particular vitamins. Even a slight lack of Vitamin C, for example, the vitamin most plentiful in fresh fruit and vegetables, is thought to increase significantly our susceptibility(敏感度) to colds and influenza.
The vitamins necessary for a healthy body are normally supplied by a good mixed diet, inclu- ding a variety of fruit and green vegetables. It is only when people try to live on a very restricted diet, say during extended periods of religious fasting(斋戒), or when trying to lose weight, that it is necessary to make special provision to supply the missing vitamins.
单选题
Scurvy is a disease that is provoked by ______.
【正确答案】
C
【答案解析】根据文章第一段第五至六行中Gradually it came to be realized that scurvy was caused by some lack in the sailors’diet(渐渐地，人们知道了坏血病是由海员食物中缺少某些成分而造成的)，可以得出C)为答案。
[避错指导] A)“腌肉和饼干”，这不是根本原因，根本原因在于没有同时搭配食用其他富含维生素的食品；B)“疲惫”，文中并未提及疲惫与坏血病的关系；D)“缺少新鲜蔬菜和水果”，也不是根本原因。
单选题
In the last sentence of Paragraph 1, "warded off" could probably be replaced by ______.
【正确答案】
C
【答案解析】根据文章第一段最后一句话的前半部分scurvy was caused by some lack in the sailors’diet(坏血病是由海员食物中缺少某些成分而造成的)说出了病因，后半部分山and引导并列句表示递进关系，说出了防治的办法scurvy could be warded off by the provision Of fresh fruit for the sailors(可以通过向海员提供新鲜水果来防治缺血病)，所以答案为C)。
[避错指导] A)“免除，除去”；B)“杀死，消灭”；D)“清除”，均为错误选项。
单选题
To avoid such disease as scurvy, it"s better for us ______.
【正确答案】
D
【答案解析】根据文章第三段第一句话The vitamins necessary for a healthy body are normally supplied by a good mixed diet，including a variety of fruit and green vegetables．(健康的身体所需的维生素一般可以通过饮食的合理搭配来提供，包括各种水果和绿色蔬菜。)所以答案为D)。
[避错指导] A)“不要吃太多腌肉”；B)“用各种维生素药片来辅助饮食”；C)“多吃新鲜水果和蔬菜”，均为错误选项。
单选题
Based on the passage we can safely conclude that if our diet is not comprehensive enough______.
【正确答案】
B
【答案解析】根据文章第二段第一句话Nowadays it is understood that a diet which contains nothing harmful may
yet result in serious disease if certail important elements are missing．(如今人们弄清楚了，饮食中如果缺少了某些重要成分，既使这种饮食中不含有害成分，也同样会导致严重的疾病。)分析各选项可知，只有B)项合适。
[避错指导] A)“维生素药片将不管用”，这种说法有悖常识；C)“蔬菜叶可以作为很好的补充”，这种说法也不够准确；D)“宗教斋戒也许能帮很大的忙”，根据文章最后一段最后—句，斋戒期间因饮食受到限制，反倒应该注意设法补充维生素的缺尖，因此D)错误。
单选题
Which of the following sentences best expresses the central idea of the passage?