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
A. not to eat much salted meat
B. to supplement our diet with various vitamin pills
C. to have more fresh fruit and vegetables
D. to develop a good dietary habit
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