小河与大海

    秋天，河水上涨，河面变得宽阔了。小河觉得天底下只有自己最大了。

    他得意洋洋地流向大海，想和大海比一比谁大。

    小河这样一边得意地想着，一边走着，别提多高兴了。一路上，他仰着头，挺着胸，兴奋地翻着浪花，唱着欢乐的歌。

    到了大海，只见一片汪洋，往远处看，天连着海，海连着天，小河用尽全身力气，抬起脚跟，怎么也看不到对岸。他懊丧地自言自语说：“我以为自己很大，原来海比我大得多。” 大海听了，笑着说：“不错，我是比你大得多，可是如果没有无数江河流到我这里，我也不会有这么大呀。”

    小河听了，更佩服大海了。

    Family values are principles that help to define us as human beings. These values are learned, usually passed down____ one generation to another. However, they can also change over time____(depend) upon the circumstances in which families find themselves. They shape the way we behave, they help families stick together, and they give us our identity.

    We always admire a person____ treats the elderly with respect, or helps people in need, or is always honest with others. Such____ (admire) behavior is usually a direct result of the values that person was taught by his family.

    These values or principles—respect, fairness and____(honest) among many others—also help hold the family together in times of trouble. When problems arise, the family is able to withstand them because they share____ same idea about____ is important. When family members feel pressure from the outside world, they know they can come into their family for a comforting connection.

    Finally, family values make us who we are____we talk about our personal character and what____ (influence) our decisions, we do so based on the values ____ (give) to us by our family.

以下各装置能完成相应实验的是（     ）

         ① 检查装置气密性         ②收集氧气           ③比较催化效果                      ④检验氧气

如图，在⊙O中，弦BC=1，点A是圆上一点，且∠BAC=30°，则⊙O的半径是 ____．