侯氏制碱法所得的纯碱中常含有少量氯化钠，现用如图所示装置来测定纯碱样品中碳酸钠的质量分数（铁架台、铁夹等固定装置已略去）．

实验步骤如下：

①按图连接装置，并检查气密性；

②准确称得盛有碱石灰（固体氢氧化钠和氧化钙的混合物）的干燥管D的质量为83.4g；

③准确称得6.0g纯碱样品放入装置B的广口瓶中；

④打开装置B的分液漏斗旋塞，缓缓滴入稀硫酸，至不再产生气泡为止；

⑤打开弹簧夹，往试管A中缓缓鼓入空气数分钟，然后称得干燥管D的总质量为85.6g．

试回答：

    One sunny Sunday morning, Alex and Emma were playing football in the park. Their dad was sitting on a chair, reading a newspaper.

    Then Emma stopped and walked to Alex. “It's too hot,” she told him. “I think I need a sun hat.” “Me too!” Alex agreed.

    Emma looked at her dad's newspaper and said, “I have an idea.” She asked Dad for two sheets of newspaper and made each of them into a hat. Then she put one on Alex's head and the other on hers. “The hat is great!” Alex said.

    They sat down next to Dad and watched everyone in the park. Then the wind began to blow. Some people started flying kites. “I wish I had a kite,” Alex said. “Or a plane!” Emma said. She took off their hats and made them into two planes.

    They played with their planes until they heard thunder (雷声). “Oh, it's time to go home now,” Emma said. “Or all of us will get wet even if I make each of us a paper umbrella!”