The vitamins necessary for a healthy body are normally supplied by a good mixed diet, including a variety of fruits and green vegetables. It is only when people try to live on a very restricted diet, say that when trying to lose weight, that it is necessary to make special provisions to supply the missing vitamins.
　　An example of the dangers of a restricted diet may be seen in the disease known as “beri-beri”, which used to make large numbers of Eastern people who lived mainly on rice suffer. In the early years of last century, a Dutch scientist named Eijkman was trying to discover the cause of beri-beri. At first he thought it was transmitted（传播）by a germ（病菌）. He was working in a Japanese hospital, where the patients were fed on polished rice which had had the outer coverings removed from the grain. It was thought this would be easier for weak and sick people to digest.
　　Eijkman thought his germ theory was proved when he noticed the chickens in the hospital yard, which were fed on remains from the patients’ plates, were also showing signs of the disease. He then tried to separate the germ, which he thought was causing the disease, but his experiments were interrupted by a hospital official, who ordered that the rice without coverings, even though left over by the patients, was too good for chickens. It should be recooked for the patients, and the chickens should be fed on cheap, rough rice with the outer coverings still on the grain.
　　Eijkman noticed that the chickens began to recover on the new diet. He began to consider the possibility that eating unmilled rice（糙米）somehow prevented or cured beri-beri — even that a lack of some ingredient（成分）in the coverings may be the cause of the disease. Indeed this was the case. The element needed to prevent beri-beri was shortly afterwards separated from rice coverings and is now known as vitamin B. The milled rice, though more expensive, was in fact causing the disease the hospital was trying to cure. Nowadays, this terrible disease is much less common thanks to our knowledge of vitamins.
According to the passage, a good mixed diet ________.

A．is suitable for losing weight	B．should be only fruits and vegetables
C．normally contains enough vitamins	D．is often difficult to arrange

What do we know about the disease beri-beri?

A．It killed large numbers of people.	B．It resulted from lack of vitamins.
C．It was transmitted by milled rice.	D．It was caused by diseased chickens.

What can be the best title of the passage?

A．A Good Mixed Diet	B．New Discovery
C．The Dangers of Beri-beri	D．The Importance of Vitamins