某少数民族自治县自治条例第一条规定：根据《中华人民共和国宪法》《中华人民共和国民族区域自治法》和有关法律法规的规定，结合本自治县政治、经济和文化的特点，制定本条例。这一规定（    ）

①表明坚持国家统一领导是民族区域自治的前提和基础

②说明制定自治条例是自治机关行使变通执行权的体现

③有利于更好地保障该县少数民族人民当家作主的权利

④反映了民族区域自治制度具有坚实的社会和政治基础

增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1）每处错误及其修改均仅限一词；

2）只允许修改10处，多者（从第11处起）不计分。

    Living without an aim is like sailing without compass. If there is no aim, we will get lose. Last term, I couldn't accept the truth which I failed in my math examination. I decided to give it up, so I skipped from classes frequently. Considered my case, my teacher offered me several detailed approach and advised me to set a short-term goal to improve my math. Finally, I work harder than ever and made great progress in her math. In my opinion, success lies in a series of goals. However, we should remember to make our targets clearly and try our best to realize our dreams.

血红蛋白是个大分子，已知血红蛋白的相对分子质量是68000，且铁元素的质量分数是0.33%，则一个血红蛋白分子中铁原子的个数为____。

﹣2015的绝对值是（　　）