填空题

Vitamin D is important for health and (11) . It is used by the body to form strong bones and teeth. That is why growing children need it. Vitamin D is called the (12) vitamin. It forms when the skin is bared to the sun. Long before people knew what vitamin D was, they learned that sunshine was important. Poor children lived in (13) slums. And they were often ill with rickets (软骨病). Rickets is a children’s disease caused by (14) vitamin D provided by sunshine, fresh milk, etc. It makes the bones become (15) and bent. In England a tax was once placed on windows. Builders put few windows in houses. Rickets became so common that it was called the English disease. Vitamin D is important for health and (11) . It is used by the body to form strong bones and teeth. That is why growing children need it. Vitamin D is called the (12) vitamin. It forms when the skin is bared to the sun. Long before people knew what vitamin D was, they learned that sunshine was important. Poor children lived in (13) slums. And they were often ill with rickets (软骨病). Rickets is a children’s disease caused by (14) vitamin D provided by sunshine, fresh milk, etc. It makes the bones become (15) and bent. In England a tax was once placed on windows. Builders put few windows in houses. Rickets became so common that it was called the English disease.