在一个高30厘米，底面半径是6匣米的圆柱形容器中盛满水，且水中浸没了一个底面半径是3厘米的圆锥形铁锥，铁锥被取出后，水面下降了2厘米。这个圆锥形铁锥的高是____厘米。

一批水果重 $\frac{3}{5}$ 吨，5天卖完，平均每天卖____吨（用小数表示），平均每天卖这批水果的____.（填分数）．

多基因遗传病是一类在人群中发病率较高的遗传病。以下疾病属于多基因遗传病的是
①先天性心脏病 ②21三体综合征 ③抗维生素D佝偻病 ④青少年型糖尿病

根据短文内容，从A、B、C、D四个选项中选择一个最佳答案。
Passage 1
     Steven Jobs, the designer of Apple Computer, was not clever when he was in school. At that time, he was not a good student and he always made troubles with his schoolmates. When he went into college, he didn't change a lot. Then he dropped out（退学）. But he was full of new ideas.
　 After he left college, Steven Jobs worked as a video game designer. He worked there for only several months and then he went to India. He hoped that the trip would give him some new ideas and give him a change in his life.
　 Steven Jobs lived on a farm in California for a year after he returned from India.
　 In 1975, he began to make a new type of computer. He designed the Apple Computer with his friend in his garage. He chose the name “Apple” just because it could help him to remember a happy summer he once spent in an apple tree garden.
His Apple Computer was so successful that Steven Jobs soon became famous all over the world .
He often said, “I live in order to change the world, there aren't any other reasons. The only way to have a great achievement is to love your own career. If you can't find your  favorite career ,go on looking for it and never give up.”
     This is Steven Jobs, though he is dead, his spirit and achievements still influence our lives.

To keep children away from danger，we warn parents ________ children at home alone．