下列化学式既能表示物质的组成，又能表示物质的分子式的是（      ）

《剑桥古代史》中描述：希腊人“不仅可以享受阿提卡的橄榄油和葡萄酒，而且可以食用黑海的谷物和干鱼，品尝腓尼基的椰枣和西西里的干酪。”这种饮食特点形成的主要原因是（    ）

    ①The Internet is becoming more and more popular. It brings us a lot of fun and convenience, ②但它也引起一些新的问题。 Children like the Internet. They would rather communicate with others online than talk with their parents.

    On the one hand, in my opinion, the Internet brings people closer. On the other hand, ③如果我们花太多的时间在网络上, we will have less time with our families and friends in the real world.

    ④Parents are always staying with us. So why not talk to them face to face when we have problems. If so, ⑤I'm sure that we can get on well with our parents.