When he was about 20 years old, O. Henry went to Texas. There he tried different ___6___. He first worked on newspaper, and then had a job in a ___7___. When some money went missing from the bank, O. Henry was believed to have stolen it. Because of that, he was ___8___ to prison（监狱）. ___9___ the three years in prison, he learned to write short stories. After he got out of prison, he went to New York and went on writing.

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Building strong bones needs calcium（钙）vitamin D and exercise starting in childhood． Here are guidelines on how much calcium and vitamins youngsters need:

1．Young children should have about 800 milligrams a day．But between ages 9 and 18, when bone growth speeds up, that should almost double． That's about three cups of milk together with calcium-rich foods, such as broccoli and cheese．

Children find teenagers need at least 200 international units of vitamin D． Milk and orange juice are often fortified（强化） with this vitamin; a few other, foods contain it． Sunlight is a major source． 2．About 10 to 15 minutes of sunshine weekly is enough for many children． The goal is to get just enough sun for vitamin D production, while avoiding too much of its skin-damaging rays．

Children of all ages need about an hour of physical activity most days．Weight--bearing（承载）exercises strengthen bone, anything from team sports like soccer to simply jumping ropes or running around． 3．The use is for tile arms or lees to bear all the body's weight．