阅读理解
It is most difficult for parents to decide whether to have a second child or not. It is often heard that a single child is likely to be a lonely child. There are no other children in the family for the child to talk to or play with. An only child is not able to get along well with children of his age. Some parents feel sad about making the decisions to have only one child.
But the number of parents choosing to have only one child is increasing in many parts of the world. In the US, for example, more than14 percent of women between 18 and 34 plan to have just one child . The same can be seen in the UK. In Japan, the average(平均) number of children born per family had gone down to 1.42 by 1996. For some single-child parents, especially who are busy working every day, time and energy seem to be overwhelming. They don't have enough time and energy to share with more children. For other people, money is their first consideration. Many couples in Japan choose not to have large families as the cost of supporting a child up to the age of 18 reaches around $160,000.
向圆C:
引切线,则切线长的最小值为( )
