下列分子式只能表示一种物质的是

根据短文内容判断下列句子正误。

    Look! It's my school dining hall．We are here for lunch every day．Before，there were many tall trees．Ten years ago，there was only a small house in my school．There was no library or computer．The playground was also small．

    Now，my school is very beautiful．The playground is big．The grass is green．We have PE and play sports on it．There is a nice teaching building in my school．It has six floors．The computer rooms are on the fourth floor and the library is on the sixth floor．We read books in the library and use the Internet in the computer rooms．

用N_A表示阿伏加德罗常数，下列说法正确的是：         

听句子,选择你所听到的信息（   ）

尽管2012年的“双十一”促销天猫和淘宝创出了单日成交量突破191亿元的惊人业绩，但对于淘宝数百万的中小卖家而言，拼服务而不是价格仍是他们长久发展的根本之计，因此不少淘宝店铺的宣传中都会有这么一句话：“您的满意，是我们永远的追求！”从经济生活看，这（   ）
①是市场调节自发性的体现       ②由企业的逐利本质决定
③是价值规律作用的结果        ④体现了社会主义的本质