题目

Childhood is a happy time, right? Not necessarily. Consider these facts. Depression(抑郁症) may occur in as many as 1 in 33 children. Once a child has an episode(一段情节) of depression, he or she has a 50 percent chance of experiencing another episode in the next 5 years. Suicide(自杀) is the 6th leading cause of death for 5–to–15-year-olds. If your child experiences 5 or more of these signs or symptoms(症状) for at least 2 weeks, he or she may be experiencing depression or another mental illness. Feeling——Does your child demonstrate: Sadness Emptiness Hopelessness Guilt Wo如图把半径是1的三个球，两两相切地放在桌面上，在上面再放一个球，使其与前三个球相切，已知第四个球的最高点与桌面的距离是3，求第四个球的半径．