The first telephone cards, produced in 1976, were Italian. Five years later the first British card appeared, and now you can buy cards in more than a hundred countries. People usually start collecting cards because they are small and light and you do not need much space for them. It is also a cheap hobby for beginners, although for some people it becomes a serious business. In Paris, for example, there is a market where you can only buy telephone cards, and some cards cost up to ￡4,000.The first Japanese card has a value of about ￡28,000. Most people only see cards with prices like these in their collectors' magazine.

2011年7月2日，杭州“最美妈妈”吴菊萍奋力接住了从10楼坠落的两岁妞妞，据估算接住妞妞需要承受约2950牛顿的冲击力，2950牛顿保留两个有效数字约为（　　）

用新鲜的大豆绿叶进行如图装置所示的实验（二氧化碳会被NaOH吸收），将其置于充足的光照下，分析D处的气体成分最可能发现（    ）

把抛物线y=x²+bx+c的图象向右平移3个单位，再向下平移2个单位，所得图象的解析式为y=x²-2x+3，则b+c=（   ）．