一本数学课本放在课桌上，开始时是封面正面朝上，翻动1次后，____ 面朝上；翻动2次后，____ 面朝上．当这本书翻动50次后，____ 面朝上，翻动2005次后，____ 面朝上．

1997年，第一只“克隆羊”在英国诞生，“克隆羊”的关键技术之一是找一些特殊的酶，它们能激活普通体细胞，使之像生殖细胞一样发育成个体，下列有关酶的叙述错误的是(   )

①思想道德修养有助于促进科学文化修养的提升

②思想道德修养是价值观的集中体现，影响科技运用的方向

③世界观、人生观、价值观是文化素养的核心，对实践活动具有导向作用

④良好的思想道德修养，有助于运用科学知识造福社会

写出下列符号
（1）三个碳酸根离子____ ，  （2） 氧化铁 ____ 。

阅读理解

Ann：My hobby is reading．I can learn a lot from different kinds of books．But that's not the only reason why I like reading．The other reason is that there are many stories in books．I always lose myself in the wonderful world that books show me．So friends，why not join me in reading books?Let's have fun together．

Bob：I used to be a bit weak，but now I'm strong because of doing sports．I do sports every day，such as running，swimming and playing bail games．I keep exercising for at least two hours a day．Whenever I feel tired，I do sports．That can make me relaxed．Then I can study better．Doing

sports is really a great hobby．