某非金属元素的原子核外最外层电子数是次外层电子数的一半，该元素

   Television is good. You’d like to watch it all day and all night. But too much TV is a very bad thing. Scientists found that kids who watch too much TV may have more trouble learning to read. They can’t focus on their work.
   Kids learn language skills best by reading, talking and playing with others. If they spend too much time watching TV, they’ll have less time for those things. Watching too much TV is bad for people’s health. People don’t move much while watching TV. What’s more, they may eat a lot of food while watching. This can make them fat. We call these people couch potatoes.
   Fighting on TV is a big problem for kids. Yong people are good at following. Scientists have found that those who watch a lot of fighting shows are more likely to fight.

1654年，马德堡市长和他的助手做了著名的“马德堡半球实验”．实验中，他们把两个铜半球壳灌满水后合在一起，再把水全部抽出，两个铜半球就会紧紧地压在一起，这证明了____的存在．小明和小强在老师的帮助下，用底面积为500cm²的平底压力锅代替铜半球模拟上述实验，当锅两边受到的拉力均为4000N时，锅恰好被拉开，此时锅内外的气压差为____Pa．如果在高原上进行这个实验，拉开这两口锅所用的拉力将____（选填：“增大”、“减小”、“不变”）．

东北平原和内蒙古高原之间的山脉是（   ）

目前，我国国内生产总值（GDP）已经超过日本，成为世界第二大经济体，但是我国人均国内生产总值仍然排在世界百名之后。由此可见（  ）
①我国全面建设小康社会的目标已经实现    ②我国仍然属于发展中国家
③我国是推动世界经济发展的唯一力量       ④我国仍然处于社会主义初级阶段